TEACHING WEED SEEDLING IDENTIFICATION AND CROP

Teaching weed seedling identification and crop staging and a survey of weeds in peppermint fieldsby Kristi Marie Carda

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science inAgronomyMontana State University© Copyright by Kristi Marie Carda (1992)

Abstract:Many farmers, ranchers, chemical dealers and chemical distributors don't know how to identify weedseedlings or stage small grains properly. If seedlings are not identified correctly and in a timelymanner, correct herbicide selection is difficult. Correct staging of small grain crops is also extremelyimportant since many of the herbicides available for use today require application at the proper cropgrowth stage to prevent crop damage.

An educational program was designed for both weed seedling identification and crop staging. Eacheducational program was designed to be easily transportable. The weed seedling identification and cropstaging workshops each included "hands-on" learning experiences which help adults learn difficultconcepts.

Weed seedling identification workshops were conduct in 23 locations around Montana during Apriland May, 1991. Crop staging workshops were also conducted in several locations around Montanaduring the fall of 1991 and the spring of 1992.

The success and popularity of the weed seedling identification and crop staging workshops indicatesthe need for more "hands-on" type workshops that relate to weed science as well as other areas.

TEACHING WEED SEEDLING IDENTIFICATION AND CROP

STAGING AND A SURVEY OF WEEDS IN PEPPERMINT FIELDS

by

Kristi Marie Carda

A thesis submitted in partial fulfillment of the requirements for the degree

of

Master of Science

in

Agronomy

MONTANA STATE UNIVERSITY Bozeman, Montana

December, 1992

I

IIS'?#ii

APPROVAL

of a thesis submitted by

Kristi Marie Carda

This thesis has been read by each member of the thesis committee and has been found to be satisfactory regarding content, English usage, format, citations, bibliographic style, and consistency, and is ready for submission to the College of Graduate Studies.

Date Chairperson, Graduate/Committeete/Coi

Date

Approved for the M^jqr Department

Head, Major Department

Approved for the College of Graduate, Studies

\ ) M j —Date Graduate Dean

iii

STATEMENT OF PERMISSION TO USE

In presenting this thesis in partial fulfillment of the requirements for a

master's degree at Montana State University, I agree that the Library shall

make it available to borrowers under rules of the Library.

If I have indicated my intention to copyright this thesis by including a

copyright notice page, copying is allowable only for scholarly purposes,

consistent with "fair use" as prescribed in the U.S. Copyright Law.

Requests for permission for extended quotation from or reproduction of this

thesis in whole or in parts may be granted only by the copyright holder.

ACKNOWLEDGEMENTS

I would like to express my sincere appreciation to my advisor, Dr. Pete

Fay, for all the help and encouragement offered during my education.

I would also like to thank the other members of my committee. Van

Shelhamer, Dave Zamora and John Lacey for their assistance and direction.

Thanks also to the members of the weed crew, Ed Davis, Dawit

Mulugeta, Phil Trunkle, Josette Wright, Michelle Christenson, Kevin Allen,

and Koy Holland for their enthusiastic support, help and advice. Without

their help, this project could not have been completed.

A very special thanks goes out to my husband, Michael for all his

support and encouragement during this project.

TABLE OF CONTENTS

Page

APPROVAL....................................................................................................................ii

STATEMENT OF PERMISSION TO U S E ................................................................ ill

V IT A ......................................................................................................... iv

ACKNOWLEDGEMENTS........................................................................................... v

TABLE OF C O N TEN TS................... vi

LIST OF TA B LE S ................................................................................................... vii

LIST OF FIGURES ................................................................................... ix

ABSTRACT...................................................................................................... .. . . . x

Chapter1. LITERATURE REVIEW ................................. I

Weed Seedling Identification..................................................................... ICrop Staging ..............Peppermint Production

Insects ................................ 12Nematodes........................................................................................... 13Diseases ........................................................................................... 14

2. WEED SEEDLING IDENTIFICATION .............................................................. 15In troduction.........................................................................................................15Methods and M aterials.......................................... 16Results and Discussion ....................................................................................17

3. CROP STAGING ..................................... 29In troduction.........................................................................................................29Methods and M aterials..................... . . . . .............................................. . 3 0Results and Discussion .................. 31

4. A WEED SURVEY OF PEPPERMINT FIELDS IN THE FLATHEADVALLEY, MONTANA ................................................ 41In troduction............................. 41Methods and M aterials.................................................. 42Results and Discussion ................................................................................... 47

5. S U M M A R Y ................................................................ 58REFERENCES CITED ........................ 86APPENDIX ........................................................................................................... 90A Teaching Guide for Weed Seedling Identification ...................................91

vi

CO N

S

Table Page

1. The principal and secondary growth stages of theZadok scale............. .................................................................. 6

2. Proposed decimal code of development for wild oats(Avena fatua L . ) ................ ............................. ............ .. 8

3. Weed species included in the broadleaf weed seedlingkey................................................................................................. 22

4. A planting date calendar for eighteen weed species . . . 23

5. Dates and locations of weed seedling identificationworkshops............................................................. ................... 27

6. Planting dates for growing small grains in thegreenhouse................................................................................. 30

7. The thirteen major production problems as perceived bypeppermint producers in the Flathead valley................. 48

8. The thirteen'weed species perceived to be the mosttroublesome by peppermint producers in the Flathead va lley .......................................................... 50

9. Crop rotations before and after peppermint production. 53

10. Cultural practices used during peppermint production . . 55

11. Seedbed preparation practices used before plantingpeppermint........................................................... ..................... 55

12. Frequency, occurrence, density, and relative abundanceof 40 weed species common to peppermint fields surveyed in 1 9 9 1 ...................................................................... 59

vii

List of Tables

(Continued)

viii

List of Tables, Continued

Table Page

13. Frequency, occurrence, density, and relative abundance of 40 weed species common to first year peppermint fields surveyed in 1991........................................................ 65

14. Frequency, occurrence, density, and relative abundance of 40 weed species common to second year peppermint fields surveyed in 1991................................... 69

15. Frequency, occurrence, density, and relative abundance of 40 weed species common to third year peppermint fields surveyed in 1991. ................................................... . 73

16. Frequency, occurrence, density, and relative abundance of 40 weed species common to fourth year peppermint fields surveyed in 1991................................................... .. . 76

17. Frequency, occurrence, density, and relative abundance of 40 weed species common to six year and older peppermint fields surveyed in 1991................................... 79

18. Field age, weed density, number of species, and weed control practices used in 34 peppermint fields surveyed in 1 9 9 1 ........................................................................... .. . . . 83

Figure Page

1. The broadleaf weed seedling key........................................ 18

2. Small grain staging pamphlet used for proper herbicideapplication using the Zadok scale........................................ 33

3. The "M" surveying pattern used to ensure each fieldwas uniformly and randomly sampled................................ 42

4. The number of years farmers have been in peppermintproduction................................................................................ 47

ix

List of Figures

V

ABSTRACT

Many farmers, ranchers, chemical dealers and chemical distributors don't know how to identify weed seedlings or stage small grains properly. If seedlings are not identified correctly and in a timely manner, correct herbicide selection is difficult. Correct staging of small grain crcips is also extremely important since many of the herbicides available for use today require application at the proper crop growth stage to prevent crop damage.

An educational program was designed for both weed seedling identification and crop staging. Each educational program was designed to be easily transportable. The weed seedling identification and crop staging workshops each included "hands-on" learning experiences which help adults learn difficult concepts.

Weed seedling identification workshops were conduct in 23 locations around Montana during April and May, 1991. Crop staging workshops were also conducted in several locations around Montana during the fall of 1991 and the spring of 1992. _

The success and popularity of the weed seedling identification and crop staging workshops indicates the need for more "hands-on" type workshops that relate to weed science as well as other areas.

ICHAPTER I

LITERATURE REVIEW

Weed Seedling Identification

The cost of weed control is a significant annual expenditure for small

grain producers. Proper and timely identification of weed seedlings is needed

to obtain efficient weed control. Unfortunately, farmers in Montana, and

elsewhere, are often not proficient at identifying weed seedlings. Effective

techniques for teaching weed identification need to be developed.

Most plant identification keys are ineffective for seedling identification

since they require flowering plants. Once weeds reach the flowering stage, it

is too late for weed control to provide benefit. However, it is useful to identify

weeds at maturity Since the weeds that are present one year will most likely be

a problem the next cropping season (Cramer, 1980).

Identification of weeds when they are small insures that the proper

herbicides can be selected for application (Lindquist, 1989). Also, chemical

control of weeds is usually more effective when seedlings are small (Stucky,

1984).

It can be very difficult to identify weeds while in the cotyledon stage

since plant morphology changes profoundly as plant development occurs

(Stucky, 1984). Agricultural producers often have difficulty making the

connection between seedling and adult plants.

2

Crop Staging

- Staging of small grain crops is important since it permits farmers and

ranchers to apply herbicides, insecticides, and fungicides at the proper time.

Correct timing of application insures the chemical will be most effective and

cause the least amount of crop damage. Unfortunately losses are all too

common in Montana from crop injury resulting from improper application timing.

Growth is defined as an increase in plant dry matter production (Kirby,

1986). The rate of growth of a cereal plant is partially dependent upon growing

conditions so the higher the temperature or the longer the daylength, the more

quickly development occurs. As the plant accumulates biomass, development

becomes complex. However, the life cycle of a small grain plant can be divided

into distinct phases which are easily recognized upon inspection (Kirby, 1986).

Resting small grain seed contains a fully developed shoot with three or

four leaf initials, and an apical dome enclosed within the coleoptile (Kirby,

1977). After imbibition, root development occurs followed by coleoptile cell

elongation (Kirby, 1986). Coleoptile elongation continues until emergence from

the soil. Leaf primordia production continues, and the initials formed may

develop into leaves, tillers or ears depending on where they are formed (Kirby,

1986; Nerson, 1980). The first three to ten primordia form leaves, while the

remaining primordia differentiate into elongated internodes or axillary (tiller)

bud's (Kirby, 1977). During early growth, excess ear and tiller primordia are

produced which die if resources become limiting (Kirby, 1977; Rawson, 1969).

3

The first true leaf of the seedling plant emerges from the tip of the

coleoptile soon after it emerges from soil. If the seed is sown deeply, the

internode between the coleoptile and the first leaf elongates which places the

crown of the plant just below the soil surface. This elongation does not occur

if the seed is planted close to the soil surface (Kirby, 1986; Martin, 1990).

Emergence of the first leaf from the coleoptile marks the transition from

the germination phase to the vegetative phase. The vegetative phase lasts until

three to six leaves have emerged on the main shoot, and all leaves and

spikelets have been produced (Kirby, 1986). The primordia develop rapidly and

accumulate in the shoot apex during the initial growth phases. When the shoot

apex has reached approximately 0.5 mm in length, ear or floral initiation takes

place. This represents the transition period between the vegetative and the

floral initiation phase. Even though there may be several days to several weeks

between the first floral initiation (main tiller development) and the last floral

initiation (secondary tiller development), plant development is somehow

synchronized so that all fertile florets develop and ripen within two to three

days of each other.

The initiation and development of tillers also takes place during this time.

The shoot apex of each tiller has the potential to produce an ear. The yield

potential of the plant is determined by the development of the main shoot and

4

tillers (Kirby, 1977). When a small grain plant is in the tillering stage, herbicide

application must be made at the correct time since improper or untimely

application often results in crop damage and subsequent yield loss (Rawson,

1969).

Tiller initiation begins with growth of meristematic tissue located at the

axil of a basal leaf. As growth of the meristematic tissue occurs, a prophyll

develops. Its function is similar to the coleoptile since it protects the newly

emerging growing point until it emerges from the leaf sheath. The tiller then

develops in a manner similar to the main shoot (Kirby, 1986).

The pattern of tiller development in wheat and barley is similar. Tillering

normally begins when a plant reaches the three leaf stage. A tiller bud

develops in the axil of the coleoptile. Additional buds develop in the axil of each

basal leaf (Kirby, 1986). Tiller bud initiation on the main stem ceases when

culm elongation begins. Tillers will then begin development at the base of

primary tillers, producing secondary and tertiary tillers.

A barley plant with 9 leaves will contain a maximum of five primary tillers

consisting of a coleoptile tiller and four primary tillers which emerge from each

of the four basal leaves. Numerous secondary and tertiary tillers may emerge

from the primary tillers depending upon growing conditions.

The first primary tiller produced may become almost as.large as the main

shoot tiller. The primary, secondary, and tertiary tillers produce fewer leaves

than the main shoot which is partially responsible for the synchronized

5

development of shoots which permits ear emergence, flower fertilization, and

seed ripening to take place almost simultaneously (Kirby, 1986). Stress caused

by drought, shading, temperature extremes, or nutrient deficiency will cause

some of the secondary and tertiary tillers to abort (Davidson, 1990). While

small grain plant development is complicated and not easily understood, staging

of small grain crops is routine and easily taught. Still, few producers stage

their small grain crops prior to herbicide application.

There are several methods used to stage small grain plants including the

Haun method, the ,Peeke's scale, and more recently, the Zadok's scale

(Davidson, 1990; Martin, 1990), which is an expansion of the Peeke's scale

(Zadoks, 1974). The Zadok scale was developed in an attempt to standardize

an internationally recognized scale for recording cereal growth stage (Table I ).

The Zadok scale divides the life cycle of a small grain plant into ten growth

stages which are further broken down into ten secondary growth stages

(Tottman, 1977; Zadoks, 1974).

This scale can be used for wheat (Triticum aestivum), barley (Hordeum

vulgare) and oat (Avena sativa) plants, and has been adopted for use with rice

{Oryza sativa) (Zadoks, 1974). Adaptation was necessary because rice is a

transplanted crop in some parts of the world, and transplanting alters

development slightly.

6

Table I . The principal and secondary growth stages of the Zadok scale (Zadoks, 1974).

Germination 5 InflorescenceOO Dry Seed 5001 Start of imbibition 51 First inflorescence just visible .02 5203 Imbibition complete 53 % o f inflorescence emerged04 5405 Radicle emerged from caryopsis 55 'A of inflorescence emerged00. 5607 Coleoptile emerged from caryopsis 57 % of inflorescence emergedOS 58 x Inflorescence fully emerged09 Leaf just at coleoptile tip 59

Seedling growth 0 Antheslo (flowering)10 First leaf through coleoptile 0011 First leaf unfolded 61 Beginning of anthesis12 2 leaves unfolded 6213 3 leaves unfolded 6314 4 leaves unfolded 8415 5 leaves unfolded 65 Anthesis half-way16 6 leaves unfolded 6617 7 leaves unfolded 6718 8 leaves unfolded 6819 9 or more leaves unfolded 69

Tillering 7 MHk development20 Main shoot only 7021 Main shoot and I tiller 71 Caryopsis water ripe22. Main shoot and 2 tillers 7223 Main shoot arid 3 tillers 73 Early milk24 Main shoot and 4 tillers 7425 Main shoot and 5 tillers 75 Medium milk26 Main shoot and 6 tillers 7627 Main shoot and 7 tillers 77 Hard dough28 Main shoot and 8 tillers 7829 Main shoot and 9 or more tillers 79

Stem elongation 8 Dough development30 Ear at I cm 8031 First node detectable 8132 2nd node detectable 8233 3rd node detectable 83 Early dough34 4th riode detectable 8435 5th node 'detectable . 85 Soft dough36 6th node detectable 8637 Flag leaf just visible 87 Hard dough38 8839 Flag leaf Ilgule just visible 89

Booting 9 Ripening40 9041 Flag leaf sheath extending 91 Caryopsis hard (hard to divide)42 92 Caryopsis hard (not dented)43 Boots just visibly swollen 93 Caryopsis loosening in daytime.44 94 Over-ripe, straw dead, decaying45 Boots swollen 95 Seed dormant46 96 Viable seed 50% germination47 Flag leaf sheath opening 97 Seed not dormant48 98 Secondary dormancy induced49 First awns visible 99 .Secondary dormancy lost

7

The secondary growth stage codes are helpful for determining the exact

timing for correct herbicide applications. The number of leaves (codes 11-19)

and the number of tillers (codes 21,-29) per plant are especially useful.

This Scale is also useful for describing the plant stage when a certain

operation was performed (Perry, 1986; Zadoks, 1974). By using a complete

Zadok plant description, the exact plant stage is described (Perry, 1986). For

example, a small grain plant with five leaves unfolded, a main shoot and three

tillers, with the first node detectable would be classified Z = 15,23,33.

Normally, only the highest number is important for a herbicide application

(Nelson, 1990) however the other numbers could prove useful in explaining

crop damage if it occurs.

Landes and Porter (Landes, 1990) modified the Zadok scale for staging

wild oat (Ayena fatua L.) growth. The pattern of growth of this weed differs

slightly from wheat (winter and spring), barley, and rye (Table 2).

When sampling a field to determine growth stage, producers are urged

to use the "M" or zig-zag pattern to collect plants (Martin, 1990; Sanders,

1987). This method insures that collection points represent the entire field so

differences in plant development from one area to the next will be recorded.

When a collection point is reached, the "Point Method" should be used for. plant

selection (Nelson et-al, 1990). The person staging should drop to one knee and

place an index finger on the soil surface. Stage the plant nearest to your finger

to ensure a random sample.

8

Table 2. Proposed decimal code of development for wild Oatsj (Avena fatua.L.) (Landes, 1990).

Germination ' 5 Floret differentiation00 Dry seed 5001 Start of imbibition 51 Floret primordium stage: round meristem-02 atic dome above lemma initials visible03 Imbibition complete 5204 53 Stamen primordium stage: three bulges05 Radicle emerged from seed on the floret meristem visible06 5407 Coleoptile emerged from seed 55 Stamen division stage: four compartments08 clearly distinctive09 Leaf at tip of coleoptile 56

575859

Vegetative development 6 Anthosls10 First leaf through coleoptile 60Tl Apex with I leaf primordium 61 Beginning of anthesis12 "Apex with 2 leaf primordium 6213 Apex with 3 leaf primordium 6314 Apex with 4 leaf primordium 6415 Apex with 5 leaf primordium 65 50% anthesis16 Apex with 6 leaf primordium 6617 Apex with 7 leaf primordium 6718 Apex with 8 leaf primordium 6819 Apex with 9 or more leaf primordium 69 Anthesis complete

Branch formation (lot-ordor branches only) 7 MHk development20 Main axis only 7021 I branch initial detectable 71 Seed watery ripe22 2 branch initials detectable 7223 3 branch initials detectable 73 Early milk24 4 branch initials detectable 7425 5 branch initials detectable 75 Medium milk26 6 branch initials detectable 7627 7 branch Initials detectable 77 Late milk28 8 branch initials detectable . 7829 9 or more branch initials! detectable 79

Transition period 8 Dough development30 Ear at I cm 8031 8132 2nd-order branches initiated 8233 3rd order branches Initiated 83 Early dough34 4th-order brancheo initiated 8435 5th-order branches initiated 85. Soft dough36 6th-order branches initiated 8637 7th-order branches initiated 87 Hard dough38 8th-order branches initiated 8839 9th-order branches initiated 89

Spikelet differentiation 9 Ripening40 Tip of main axis undifferentiated 9041 Spikelet primordium just visible on main axis 91 Seed hard (difficult to divide)42 92 Seed hard (dented by thumbnail)43 93 Seed loosening.44 94 Over-ripe, straw dead and collapsing45 Glume primordium stage: two ridges appear at - 95 Seed dormant

right angles to the plane of I st-order branches 96 Viable seed giving 50% germination46 97 Seed not dormant47 98 Secondary dormancy induced48 99 Secondary dormancy lost49 Lemma primordium stage: prominent ridges

between glumes visible

9

Once the growth stage has been determined, the proper herbicide can be

selected. For example, wheat is susceptible to phenoxy herbicide injury from

emergence to the four-leaf stage, and from jointing to the soft dough stage of

growth (Z= 10-14 and 31-85) (Kirby, 1986). Phenoxy herbicide application at

these stages can reduce plant height, delay maturity, deform plants, reduce

yield, increase seed protein, reduce germination and reduce test weight (Nelson

et al, 1990).

Use of these scales has simplified the process of plant.staging. It is now

possible to teach chemical distributors, chemical dealers, farmers, and ranchers

to stage small grain crops accurately which permits accurate communication

when staging small grain crops.

Peppermint Production

Peppermint has been cultivated as a crop in Montana for 23 years. In

the past ten years, the number of acres in production has increased

dramatically. Peppermint is a high value cash crop that is grown and harvested

for the oil the plant contains. This oil is used for human consumption in

candies, toothpaste, and other food stuffs.

The Mentha species has been cultivated for centuries by many cultures.

It is believed that the word Mentha was derived from Menthe, a nymph who

was loved by Pluto. Pluto's jealous wife, Proserpina, transformed Menthe into

the green herb mint (Macleod, 1968).

10

The Egyptians mentioned the use of mint for medicinal purposes as early

as 2800 B.C. The Ancient Greeks used mint for scenting their bathwater, while

the Arabs offered a cup of strong mint tea as a customary gesture of

hospitality. In more recent times, Theodore Roosevelt cultivated a mint patch

at the White House for use in beverages. During prohibition, mint patches were

destroyed because the herb is used as a flavoring in an alcoholic drink

commonly served in the South - the mint julep (Bubel, 1985).

The genus Mentha is a member of the very large Labiatae family, which

includes other herbs such as sage, thyme, marjoram, rosemary, basil, and

lavender. There are approximately 25 species of mint in the world, many of

which grow wild. Only eight species are commonly grown under cultivation.

The three most common cultivated species are spearmint (Mentha viridis),

peppermint (Mentha piperita), and pennyroyal (Mentha pu/egwmXMacleod,

1968). Wild populations are common throughout the temperate regions of the

world. Mint is cultivated in Argentina, Australia, France, Germany, Great

Britain, India, Italy, Japan, Yugoslavia, and the United States. The United

States is the largest commercial source of peppermint oil in the world, and

most is produced in the Pacific Northwest (Farrell, 1985).

Mints are easily recognized by their perennial growth habit, square stem

and paired, shallowly toothed leaves. Stems grow to a height of 45 to 90 cm

with flowers appearing as spikes at the terminal ends of stems or in clusters

rising from the leaf axils. Flower color may be white, pink, or lavender. Due

11

to the shallow root system, mint plantings thrive under moist, humid

conditions. While most mint species tolerate some shading, they thrive when

grown in full sunlight. Plants grown in shade contain less aromatic oil (Bubel,

1985).

After establishment, mints produce rhizomes which aggressively invade

the area surrounding each plant. Mentha species are normally propagated by

cuttings. Mints hybridize readily and plants true to species are difficult to

obtain from seed (Bubel, 1985).

Ofthethree mint species, I will discuss peppermint {Menthapiperita),Xhs

specie grown in Montana for the remainder of this chapter. Peppermint is

thought to be a cross between spearmint (Mentha spicata) and water mint

(Mentha aquatica). Peppermint has lance-shaped leaves on short stems and

exists as two distinct strains. The first recognized strain is referred to as black

mint, and has purple-tinged stems. The second strain, is white mint, has lighter

green leaves, a more slender stem and a milder aroma and flavor (Bubel, 1985).

The volatile oil produced is used to flavor foods, medicines, tooth paste,

chewing gums, cordials, tobacco products, and liqueurs (Farrell, 1985,

Williams, 1977).

Roots are normally dug and planted in the fall in rows 60 to 90 cm apart,

on 30 cm centers.. After emergence in the spring, the rows appear sparse. A

solid stand is obtained in 2 to 3 years. Fields may need to be renovated by

12

lightly discing, corrugating, or shallow plowing to disrupt the root system which

prevents the crop from choking itself out.

Peppermint is vulnerable to insects, nematodes and diseases. An insect

that causes problems for peppermint producers is the two spotted spider mite

(Acari: Tetranychidae). The major nematode problems in the Flathead valley

of Montana include root-lesion nematode (Pratylenchuspenetrans Cobb, 1917;

Filipjev and Stekhoven, 1941), pin nematode (Paratylenchusspp.), stubby root

nematode (Trichodorusspp.), and ring nematode (Crfconemel/a spp.). Diseases

include VerticiHium wilt (VerticiHium dahiiae Kleb.) and rusts.

Insects:

The two spotted spider mite is the most widely distributed pest of

peppermint (Hollingsworth, 1982). The major damage caused by the two

spotted spider mite is injury to the cuticle and epidermal cells on leaves, which

disrupts leaf surface layers and destroys the underlying mesophyll cells.

Mesophyll damage affects the ultrastructure of the remaining mesophyll cells,

reduces gas exchange from the leaf, and reduces plant growth. Spider mite

populations are influenced by many factors including climate, intraspecific

competition, host plant condition, predators, and agricultural practices

(Hollingsworth, 1982).

Feeding injury leads to increased water loss at night, which results in

water stress during the daytime (DeAngelis, 1983). Outbreaks of two spotted

spider mites usually occur during hot, dry periods (Hollingsworth, 1982) when

13

daytime water demand is high. The resulting stress reduces production of

secondary plant products, including the essential oil monoterpines. The

epidermal disruption reduces essential oil production which is synthesized•

primarily in glandular structures located on the epidermis (DeAngelis, 1983).

Nematodes:

Nematodes, commonly referred to as roundworms, are microscopic in

size (DeAngelis, 1983; Leonard, 1991; Hollingsworth, 1982). Nematodes are

appendageless, nonsegmented, wormlike invertebrates possessing a body

cavity and a complete digestive tract (mouth, an alimentary canal, and an

anus). Nematodes vary greatly from 82 t/m to over Inm in length.

There are about 2 ,200 nematode species that attack plants which cause

approximately $5 billion in losses in the United States in 1991 (DeAngelis,

1983). Plant parasitic nematodes can be broken down into two basic groups -

ecto- or endoparasites. Ectoparasites feed on the outside of the root by forcing

their stylet (mouth-spear) into the root tissue. These nematodes remain on the

outer root surface throughout their life cycle. Endoparasites tunnel through the

root structures, spending all or part of their life cycle inside the plant tissue

leaving holes or lesions where pathogen invasion leads to further damage

(Clark, 1980; Macjeod, 1968; Williams, 1977). Some nematodes can travel

through plant tissue to attack leaves and blossoms (Clark, 1980).

14

Nematodes when unaided, can only spread 30 to 90 cm per year. They

are widely spread by movement in infested soil on shoes, tools and transplants.

Wind and water erosion can also spread nematode infestations to new locations

(Clark, 1980; Kimpinski, 1984; Poinar, 1983).

Diseases:

Verticillium wilt (VerticiHium dahliae Klebahn), a soil borne fungus, is also

a serious problem in peppermint production (Brandt, 1984). This disease has

caused abandonment of thousands of acres of highly productive land in the

midwest during the 1940s and 1950s. The disease was later spread to the

peppermint acreages in the Willamette River valley in Oregon and the

Columbian basin in Washington due mainly to the fact that new peppermint

plantings are started by using stolons from previous plantings. This forces

growers to constantly move to "new land" to prevent crop losses after the

disease had built up in the soil (Green, 1975).

Effective control of verticillium wilt is difficult and expensive. Chemical

soil fumigation provides effective, but short term control. A more effective and

more cost conscious control program can be obtained through the use of crop

rotations to alternate crops that are resistant to the disease. This helps reduce

the amount of inoculum in the soil so peppermint can be planted back into once

highly infected fields.

15

CHAPTER 2

WEED SEEDLING IDENTIFICATION

Introduction

The ability to identify weed seedlings is an important tool in crop

production. If weed seedlings are not identified correctly and in a timely

manner, correct herbicide selection is difficult. Correct herbicide selection is

becoming more complicated with the increase in herbicide resistance which

often requires that two or more herbicides be applied in a tankmix for optimal

weed control.

Correct identification of weed seedlings is routine and is best performed

by scouting fields early when weed seedlings are small. Many producers and

agribusiness personnel in Montana cannot identify weed seedlings partially

because there hasn't been an effective learning method.

The purpose of this project was to develop a "hands-on", portable

workshop to teach farmers, county agents, government employees, and

agricultural business professionals to identify weed seedlings using a simple key

and live plant material.

16

Methods and Materials

A broadleaf weed seedling key (Figure I) was developed by Nelson

(1986) which features twenty-two of the most common broadleaf weed

species found in cultivated crop land in Montana (Table 3). A workshop was

developed which combined use of the key with field quality weed seedlings.

The first objective was to develop a planting calender which would allow

enough time for weed seedlings to develop to the two leaf stage of growth

when presented to an audience.

Plastic flats 30 by 60 by 10 cm deep were filled with moist greenhouse

soil [1/3 Bozeman Silt Loam, 1/3 spagnum peat moss, 1/3 washed concrete

sand (v/v/v)] that was mixed, steam pasteurized at 90 ° C for one hour prior to

use. Seed of twenty-two species was planted in separate rows, 2.5 cm apart *

and 1.25 cm deep. The plants were grown 90 cm under 1000 watt metal

halide lights under a 24 hour photoperiod to prevent flowering. The greenhouse

was maintained at a daytime temperature of 21 ± 2° C and a nighttime

temperature of 65 ± 2° C. Flats were watered in the morning to discourage

development of powdery mildew (Erysiphe spp.). After emergence, seedlings

were watered sparingly in the morning, to control development of damping off

(Pythium spp.).

17

The number of days after planting to emergence, full cotyledon stage,

and first and second true leaf stages was recorded for each species. The

experiment was repeated twice.

A planting calendar (Table 4) was developed and maintained so that each

species was planted on the appropriate day before a workshop. Individual

seedlings in the two true leaf stage were transplanted into plastic "cell packs",

each containing six 4 by 4 by 6 cm deep cells approximately one week before

each workshop to permit recovery from transplant shock.

Results and Discussion

After the planting calender was developed, a letter was sent to each

county extension agent in Montana offering a weed seedling identification

workshop to the first fifteen agents to respond, th e initial intent was to

present workshops during April and May, 1991, however, workshops were

taught around the state for almost two years due to popularity. .

Eighteen of the twenty-two weed species on the key were used for the

workshops. The four species not included were waterpod, henbit, and hairy

nightshade due to a shortage of seed, and cutleaf nightshade which did not

germinate consistently.

Figu

re I

. Th

e br

oadl

eaf w

eed

seed

ling

key

(Nel

son,

198

6).

Broadleaf Weed Seedling KeyExtension Service Montana State University, Bozeman EB 7 Reprinted June 1989

(Con

tinue

d)

OOO

19

Figure I. The broadleaf weed seedling key (Nelson, 1986). (Continued)

BROADLEAF WEED SEEDLING KEY

BEGIN HERE

C o ty le d o n and first le a f are illu s tra ted .

Linear, lanceolate to oblong-shaped cotyledons

Ovate-sheped cotyledons

Leaves sparsely hairy or without hairEastern b lack m ghtshade

First two leaves are opposite, later leaves are alternate

Pinnate tansymustard

Plnnately Iobed leaves

Leaves NOT plnnately Iobed

All true leaves are opposite

Walerpod

All true leaves are

Leaves densely hairy A • i. )

Hairy nightshade | ' Jr

Ovale shaped leaves with pinnate venetlon

Round leaves with palmate venation

Common mallow

Leaves sparsely hairy or without hair

Leaves are very hairy

The stem Is equere above the cotyledons

The stem is round or absent;Il absent the seedling consists ol a basal rosette ol leaves

Oval, apatulate to round cotyledons

Kidney-shapedcotyledons

Wild mustard

by James E. Nelson Extension Weed SpecialistThe programs ol the Montana Stale Unrvemly E K ie n sw Servce are available io a t people regartSess of race, creed, cotot se*. handicap or national origin, issued in fu rtherance o f cooperative extension w ork in a g ricu ltu re and hom e econom cs. acts o f Mey S and June 30. 1914. m cooperation with the U S. Department of Agrcuflure. James R. Welsh. Daectoc Extension Service. M ontana State Unhenay1 Bozeman. Montana 59717.

(Continued)

20Figure I . The broadleaf weed seedling key (Nelson, 1986). (Continued)

Leevee NOT meely

Common sunflower

Cotyledon* spsrvely hairy or without heir

Cotyledons ,densely hairy

Common lambsquarters

Ovale-ehaped Ieevea

Leave* without hair

Leave* NOT needle-llke

Wild buckwheat

Arrowhead-shapedleave*

Leave* without hairMargin of second and later leaves Is entire or evenly toothed

Henbit

Leaves are opposite with 2 leaves per node

Leaf margin teeth have soft spines at the tips

True leaves are alternate

Catchweed bedstraw

Leaves are whorfed with 4 to 8 leaves per node

Russian thistle

Leaves are needle- llke

Leaves NOT arrowhead shaped

Leaf margin teeth are NOT spine tipped

True leaves are opposite

Margin of second and later leaves Is unevenly toothed or Iobed

Tumble mustard

(Continued)

21

Figure I . The broadleaf weed seedling key (Nelson, 1986). (Continued)

Idenlincalion of broadleaf vwed seedlings is critical to their control. Weed species vary in their response to herbicides; therefore it is necessary to select the right herbicide to control a particular species. Controlling weeds in the early stages of growth not only increases the effectiveness of control m easures, but also reduces crop losses due to weed competition.

This key provides an easy and reliable means for identifying broadleaf weed seedlings. Tb use the key you need to understand how the key is organized and be able to recognize a few simple characteristics used to identify broadleaf weeds.

Broadleaf seedlings must be examined with great ca/e. One characteristic seldom is sufficient to identify the weed. The following steps will help you use the identification key and insure correct seedling identification.

1. Collect several samples of the plant to be identified.

2. Use a hand lens when available to make plant characteristics easier to see.

a Begin on the left side of the key and proceed step by step to the r ig h t Do not skip any steps.

PLANT PARTS

Terminal Bud5 Laaf N

F in t LeafPalmate —r

Venation 4/ Pinnate Venation

EntireMarginStem

Mldveln Cotyledon

LEAF ARRANGEMENT ON STEM

Oppoalte Leavea Attached at same node

on opposite sides of stem. Leaves at the same node

are of simitar size

Alternate Leaves One leal per node New leaf is smaBet

COTYLEDON AND LEAF SHAPES

Oblong

Spalulate

Round Kidney

Palmalely Lobed Plnnalely Lobed

TERMINOLOGYAlternate Leaves—One leaf attached per

node Newest leaf is of smaller sizeCotyledon—Seed leaves; the first pair of

Ieafiika structures, usually paired, appearing a bo/e ground in most dicotyledonous plants.

Entire Leaf Margins— Leaf margins that are smooth without sawtoothed or irregularly notched edges.

Lobe—A division or segment of a leaf.Margin—The border or edge of any plant

part.Mealy—Covered with a smalt, white bran-like

bloom.Midvein—The central vein of a leaf.Node—That part of the stem from which

leaves or branches arise.Opposite Leaves—Leaves attached at the

same node on opposite sides of the stem. Newest leaf pair are of similar size.

Palmate—Three or more lobes or veins aris-. ing from one point

Petiole—The stalk of a leaf.Pinnate— Lobes or veins arranged on two

sides of the midvein.Rosette—A basal cluster of leaves in a cir

cular form without discernible upright stem.

Toothed Leaf Margins— Sawtoothed or irregularly notched leaf edges.

Whorled-Three or more leaves attached at the same node, often arranged in a whorl around the stem.

22

Table 3. Weed species included in the broadleaf weedSeedling key (Nelson, 1986).

Common Name Latin Name

wild mustard Brassica kaber (D.C.) Wheeler

common mallow Malva neglecta Wallr.

cutleaf nightshade . Solanum triflorum Nutt.

pinnate tansymustard Descurainia pihnata (Walt.) Britt

waterpod EHisia nyctelea L.

kochia Kochia scoparia (L.) Schrad.

hairy nightshade Solanum sarrachoides Sendt.

Eastern black nightshade Solanum nigrum L.

henbit Lamium amplexicaule L.

catchweed bedstraw Gaiium aparihe L. . .

wild buckwheat Polygonum convolvulus L,

Russian thistle Salsola iberica Sennen

prickly lettuce Lactuca serriola L.

field pennycress Thlaspi arvense L.

red root pigweed Amaranthus retro flex us L.

prostrate pigweed Amaranthus blitoides S.Wats.

common Iambsquarters Chenopodium album L.

cowcockle Vaccaria pyramidata Medic.

corn gromwell Lithospermum arvense L.

sheperdspurse Capsella bursa-pastoris (L.) Medic.

common sunflower Helianthus annuus L.

tumble mustard Sisymbrium altissimum L.

23

Table 4. A planting date calendar for eighteen weed species.

WeedSeedling

Group

Days after planting to reach

2 leaf stageWeed Species

I 33 sheperdspurse prostrate pigweed

Il 28 tumble mustard field pennycress redfoot.pigweed Eastern black nightshade

- Ill 25 pinnate tansy mustard catchweed bedstraw wild buckwheat

IV 22 Russian thistle prickly lettuce common Iambsquarters cowcockle corn gromwell wild sunflower

V . 18 common mallow

Vl 14 kochiawild mustard

24

At each workshop, the instructor taught the participants how to use the

key with the aid of a slide set which illustrated the differences in cotyledon

shape, leaf shape, and leaf arrangement on the stem. After a fifteen minute

slide presentation, the first cell pack of seedlings and a key were distributed to

each participant. The first cell pack contained the six easiest weed seedlings

to identify. The seedlings, in order of ease of identification were wild mustard,

kochia, red root pigweed, cowcockle, eastern black nightshade, and catchweed

bedstraw.

The instructor guided participants through the key to identify each weed

seedling. After successful identification of each seedling, a slide of the adult

plant was shown so producers could visually associate the seedling with the

mature, flowering plant. Many producers who didn't recognize the seedling

were surprised when the familiar mature plant was shown. After the first six

weed seedlings were correctly identified, the second cell pack was distributed.

The second cell pack included Russian thistle, common mallow, wild

buckwheat, tumble mustard, corn gromwell, and field pennycress. Participants

identified each weed seedling without help. The instructor helped only upon

request. After giving participants a few minutes to identify each plant, the

instructor went through the key to help those who incorrectly identified

seedlings. This helped participants determine where errors had occurred as

they used the key, and to answer any questions that arose. A slide of the adult

plant was shown again. This systematic process of identifying weeds of

25

increasing difficulty helped build participant's confidence. After successfully

identifying the six seedlings in each of the first two cell packs, they were

prepared for the six most difficult seedlings.

The third cell pack contained common lambsquarters, prostrate pigweed,

common sunflower, pinnate tansy mustard, prickly lettuce, and sheperdspurse.

These seedlings were used as a test to measure the competence of the

wqrkshop presenter. Each participant had to identify each weed seedling

without help from the instructor. After all identifications were made, the

instructor measured the identification success rate for each species. A slide.

showing the adult plant was again shown after each weed seedling was

identified.

Cell packs sufficient for five meetings were placed in a six-shelf rack

which fit the bed of a pickup truck covered with a fiberglass shell. Plants could

be used for more than one meeting, and as many as four participants could use

a single cell pack, so the number of plants needed for several meetings was

lower than first expected. Plants were placed inside the crew cab pickup truck

when temperatures fell below freezing.

The weed seedling identification workshop was conducted in 34

locations in Montana (Table 5). A slide set was developed in the event that

plant material was accidently lost to freezing. The slide set contained a slide. ■ ■>

of each seedling in the cotyledon to two true leaf stage along with a slide of

the mature plant. It seemed that participants were able to use the key

>

26

successfully with slides, however participants seemed to learn more when live

plant material was used because plant characteristics including hairs, spines,

and characteristic fragrances were not demonstrated.

A teaching guide (Appendix A) that included tips about each seedling

was developed for the slide set. It contained hints and important facts needed

for successfully teaching weed seedling identification. The teaching guide was

especially useful for instructors who were not initially familiar with the

seedlings.

27

Table 5. Dates and locations of weed seedling identification workshops.

Location/Conducted by Date # of Attendants

Willow Creek/Carda, Fay Jan. 22, 1991 30

Circle/Carda April 3, 1991 68

Denton/Carda April 5, 1991 .10

Lewistown/Carda April 5, 1991 8

Moccasin/Carda April 4, 1991 4

Wilsall, afternoon/Carda ' April 8, 1991 20

Wilsall, evening/Carda April 8, 1991 23

Belgrade/Carda April 11, 1991 22

Ryegate/Carda April 16, 1991 7

Roundup/Carda April 16, 1991 2

Hysham/Carda April 17, 1991 8

Forsyth/Carda April 17, 1991 4

Broadus/Carda April 18, 1991 18

Noxon/Carda April 24, 1991 3

Hot Springs/Carda April 24, 1991 3

Scobey/Carda May 7, 1991 5

Sidney/Carda May 8, 1991 8

Great Falls/Carda May 13, 1991 17

Chester/Carda May 14, 1991 15

Cutbank/Carda May 15, 1991 2

Shelby/Carda May 15, 1991 10

Conrad/Carda May 16, 1991 9

Dutton/Carda . May 16, 1991 3 6

Bozeman/Wright July 14, 1991 30

Bozeman/Carda Nov. 2, 1991 22

(Continued)

28

Table 5. Dates and locations of weed seedling identification workshops. (Continued)

Location/Conducted by Date # of Attendants

Bozeman, ICPM/Carda Jan 13, 1992 35

Roundup/Orville Moore Feb. 11; 1992 25

Kalispell, Equity Supply/Carda

Feb 12, 1992 58

Bozeman, Alfafla/Carda Feb. 18, 1992 40

Conrad, Cenex/Carda Feb. 24, 1992 45

Bozeman, Aviation/Carda Feb. 26, 1992 21

Dutton High Schoot/Brent Hitchcock

March 14, 1992 15

Poplar/Dallas O'Connor March 19, 1992 30

Bozeman, Master Gardners/Carda

May 7, 1992 5

29

CHAPTERS

CROP STAGING

Introduction

Correct staging of small grain crops is extremely important since many

of the herbicides available for use require application at the proper crop growth

stage to prevent crop damage. Producers who do not properly stage small

grain crops will often lose crop yield to herbicide injury.

When choosing the herbicide(s) to use, the weed species present in a

field and their growth stage must also be considered (Chapter 2). Identification

of these two factors, weed identification and crop staging, enables producers

to match the best herbicide for both the crop and weed spectrum which can

change both from field to field and from year to year.

Many producers in Montana and elsewhere do not stage their small grain

crops to determine when to spray. While it is difficult to estimate the income

lost due to crop damage or uncontrolled weeds, it is certainly a significant loss.

The purpose of this project was to develop a mobile, interactive

workshop to teach crop staging to producers, chemical dealers, county agents,

and others involved in cereal grain production.

30


Barley, spring wheat and winter wheat seed was planted 2.5 cm deep

every 12 cm in rows 7.5 cm apart in 45- by 90- by 7.5-cm deep flats filled

with moist soil [1/3 Bozeman Silt Loam, 1/3 sphagnum peat moss and 1/3

washed concrete sand (v/v/v)], that was steam pasteurized at 90 ° C for one

hour before using. The greenhouse was maintained at a daytime temperature

Of 21 ± 2 ° C and a fourteen hour light photoperiod; nighttime temperature

was maintained at 18 ± 2° C with a ten hour dark period. Observations from

other temperature regimes and varying photoperiods indicated this to be the

proper growing conditions. Other growing conditions resulted in plants that

were spindly and lacked general vigor..

Plants were grown to the desired stage (Table 6) and carefully pulled

from the soil. The soil was rinsed from the roots, plants were wrapped in wet

paper towels, covered with plastic garbage bags and placed in cardboard boxes

for shipping by air express or UPS for delivery the next day.

Table 6. Planting dates for growing small grains in the greenhouse.

Crop Stage Desired

Planting Date (Weeks Before Workshop)

2-3 leaf 3-4

3-4 leaf 4-5

4-5. leaf 5-6

5-6 leaf 6-7

31


Twenty-one' degrees centigrade proved to be the optimum temperature

for germination and plant development. If temperatures exceeded 21 0 C,

plants grew tall and spindly and did not tiller well.

If four-, five-, and six-leaf or larger plants, were needed, supplemental

nitrogen fertilizer was required. A solution containing Peter's fertilizer

formulation 20-10-20 with.trace elements (W.R. Grace Company, Fogelsville,

PA) was applied to soil at a rate of 100 ppm nitrogen at the three- to four-leaf

stage. Plants in later stages of development required weekly fertilization to

remain healthy.

Only fifteen seeds were planted per flat since small grain plants would

not tiller under crowded conditions. For best development after emergence,

supplemental light was necessary. Flats were located on greenhouse benches

90 cm under 1000-watt metal halide lights with a fourteen-hour photoperiod.

The lights were raised as the plants grew to maintain the 90 cm distance

between the plants and the light source. After seeding, flats were watered

every other day until emergence. When emergence occurred, flats were

watered daily, but care was taken to avoid both overwatering and drouth

stress. Water requirements increased significantly after the plants began to

tiller.

32

After the planting calendar was developed, a pamphlet was developed

that included a description of the Zadok scale (Zadok et al, 1974), a list of

definitions relating to the Zadok scale, and a chart containing the thirteen most

commonly used herbicides in Montana (Figure 2). The chart matched the

Zadok numbers with the proper time of application for each herbicide in winter

wheat, spring wheat and barley.

Barley plants were superior to wheat for teaching purposes because the

leaves are wider and less spindly than wheat leaves when produced under

greenhouse conditions. Barley tillered more readily than wheat, resulting in a

compact plant identical to field grown plants. The plants developed

approximately one leaf per week. Node elongation occurred when plant

development reached five to six leaves.

Workshops were held at several locations in the state. After evaluating

the success of the workshops, modifications were made and a training session

was held for people interested in teaching crop staging. Those in attendance

were eligible to receive plants from the author to teach crop staging workshops

in 1992. The cost of plants was $35.00 per 100 plants in the three- to four-

leaf stage, and $50.00 per 100 plants in the five- to six-leaf stage. Plants in

the latter stage were useful for demonstrating tiller production and teaching

node elongation.

Figure 2. Small grain staging pamphlet used for proper herbicide applicationusing the Zadok scale.

S tag in g S m all Grainsfo r P roper

H e rb ic id e A p p lica tio n

Using the zadok Scale

(Continued)

34

Figure 2. Small grain staging pamphlet used for proper herbicide applicationusing the Zadok scale. (Continued)

Anthesis - Flowering.Boot - Area inside sheath where seed head begins to swell before emergence from the sheath.Caryopsis - Grain kernel.Coleoptile - Protective covering over shoot. Shoot breaks through after emerging from soil.Coleoptile tiller - Tiller that arises from the seed (below the crown area). Early dough - The grain contents are soft and cheesy.Early milk - The grain contains white, watery liquid. . .Flag leaf - Last leaf to emerge before head appears.Hard dough - The grain contents are dry and cannot be squeezed out. Imbibition - The process when the seed absorbs water for seed germination.Inflorescence - The seed head.Internode - The space between nodes.Jointing = stem elongation - The growth process when the nodes begin to separate, resulting in the head emerging from the stem.Late milk - The grain contents are wet and sticky when crushed.Ligule - Membranous structure located at the base of a leaf, behind the stem.Main shoot - Largest tiller; gives rise to primary tillers.Medium milk - The grain is nearly full length and contains a soft, wet center in a watery liquid.Node - Area on the tiller where stem elongation occurs.Primary tiller - Tillers that arise in the axils of the main shoot leaves. Radicle - The root as it emerges from the seed.Sheath - Central part of stem where leaves are attached.Spikelet - Individual floret group on the seed head.Unfloded leaf - A leaf is considered to be unfolded when the Iigule has emerged from the sheath of the proceeding leaf.

(Continued)

35

Figure 2. Small grain staging pamphlet used for proper herbicide .application, using the Zadok scale. (Continued)

0 Germination00 Dry seed01 Start of imbibition02 Imbibiiion03 Imbibition complete04 Radicle emerging from seed'05 Radicle emerged from seed OS Coleoplile emerging from seed 07 Coleoplile emerged from seed OS Leaf elongating thru coleoptile09 Leaf just at coleoptile tip

1 Seedling Growth10 First leaf through coleoptile11 First leaf unfolded12 2 leaves unfolded13 3 leaves unfolded14 4 leaves unfolded15 5 leaves unfolded16 6 leaves unfolded17 7 leaves unfolded18 8 leaves unfolded19 9 or more leaves unfolded

2 Tillering20 Main shoot only21 Main shoot and I tiller22 Main shoot and 2 tillers23 Main shoot and 3 tillers24 Main shoot and 4 tillers25 Main shoot and 5 tillers26 Main shoot and 6 tillers27 Main shoot and 7 tillers28 Main shoot and 8 tillers29 Main shoot and 9 or more tillers

3 Stem Elongation30 Ear at I 'cm (pseudostem erect)31 First node detectable32 2nd node detectable33 3rd node detectable34 4th node delectable35 5th node delectable36 6th node detectable37 Flag leal just visible38 Flag leal partly emerged39 Flag leaf Iigule just visible

4 Booting40 Flag leal fully emerged41 Flag leaf sheath extending42 Boot beginning to swell ■43 Boot just visibly swollen44 Boot are swelling45 Boot swollen46 Head ready to emerge from boot47 Flag leal sheath opening48 Flag leal sheath open49 First awns visible

5 Inflorescence (ear/penlcle) emergence50 First spikelet of inflorescence visible51 First spikelet of inflorescence visible52 First spikelet emerging53 1/4 of inflorescence emerged54 1/3 of inflorescence emerged55 1/2 of inflorescence emerged56 2/3 of inflorescence emerged57 3/4 of inflorescence emerged58 Inflorescence emerged59 Pre-anthesis

7 Milk Development70 Kernel shell developed71 Kernel contents very watery72 Kernel contents turning while73 Early milk74 Kernel contents beginning to solidify75 Medium milk76 Kernel contents are wet and sticky77 Late milk78 Kernel contents are sticky79 Kernel contents are soft and sticky

818283 Early dough8485 Soft dough8687 Hard dough8889

9 Ripening90 Seed hard (thumbnail dent remains)91 Seed hard (diIlicuIt to divide)92 Seed hard (not dented by thumbnail)93 Seed loosening in daytime94 Over-ripe, straw dead and collapsing95 Seed dormant96 Viable seed giving 50% germination97 Seed not dormant98 Secondary dormancy induced99 Secondary dormancy lost

8 Dough Development 80

6 Anthesls (Flowering)60 Beginning anthesis61 62636465 Anthesis halFway66676869 Anthesis complete

(Continued)

36

Figure 2. Small grain staging pamphlet used for proper herbicide applicationusing the Zadok scale. (Continued)

H e rb ic id e W in te r W h e a t S p r in g W h e a t a n d B a r le y

A lly 2 le a f to ju s t b e fo re b o o t s ta g e S a m e as w in te r w h e a t.

Z= 12 -39 Z = I 2 -39

B anve l S G F A p p ly in sp rin g a fte r re s u m p tio n '

o f g ro w th prior, to jo in tin g .Z= 13-30

A p p ly to sp rin g w h e a t be fo re it exceeds the 5 le a f s tag e . (Z = 12 -15)A p p ly to b a rle y be fo re in e xce e d s the 4 le a f s tag e . (Z = 1 2 -1 4)

B ro n a te A p p ly a fte r 3 lea f s tag e b u t S a m e as w in te r w h e a t.

be fo re b o o t s ta g e . Z= 13-39 Z = I 3 -3 9

B uc tril F rom e m e rg e n c e up to b o o t

s tag e .Z = 1 0 -3 9

S a m e as w in te r w h e a t.

Z = 1 0 -3 9

C u rta il • F rom 4 le a f up to jo in tin g . Z = I 4 -2 9

S a m e as w in te r w h e a t. Z = I 4 -2 9

C u rta il M From . 3 le a f up to jo in tin g . Z = 13 -2 9

S a m e as w in te r w h e a t. Z = 1 3 -2 9

E x p re s s F rom 2 le a f s ta g e b u t p r io r to e m e rg e n c e o f flag lea f. Z = I 2 -3 5

S a m e as w in te r w h e a t.

Z = 12-35

H a rm o n y F rom 2 le a f s ta g e b u t p r io r Io 3 rd F rom 2 le a f s tag e p r io r to ap pe a ra n ce

E x tra n o d e s ta g e . Z = I 2 -33 o f 1 s t no d e s ta g e . Z=12-31

M C P A F rom 4 le a f s ta g e p rio r to jo in t in g . S a m e as w in te r w h e a t.

A m in e Z = I 4 -2 9 Z = I 4 -2 9

M C P A 3 to 4 le a f fu lly tille re d up to b o o t Sctm e as w in te r w h e a t.

E s te r . s ta g e . Z = 1 4 -4 2 / Z = 1 4 -4 2

T o rd o n 22K A p p ly in sp rin g a fte r re s u m p tio n o f g ro w th u n til e a rly jo in tin g .

-Z = I 3-31

3 le a f to early, jo in tin g .

Z = 1 3 -30

2 ,4 -D S p ra y a fte r tille rin g bu t b e fo re S a m e as w in te r w h e a t.

A m in e ■ jo in t in g . Z = I 4 -29 Z = 1 4 -2 9

2 ,4 -D E s te r A fte r g ra in is fu lly tille re d b u t •Sam e as w in te r w h e a t.

L V -4

L V -6

b e fo re jo in t in g . Z = 1 5 -2 9 Z = 15 -2 9

37

Once plants were removed from soil and placed in boxes for shipping,

they would remain fresh for seven to ten days if kept moist in a refrigerator

(6 to 8 ° C). One shipment of plants could be used for workshops for one

week.

Sales representatives from the Sandoz Crop Protection Corporation made

excellent use of the plants. They conducted 65 workshops over a four month

period in 1992 using plants in the three- to four- and five- to six-leaf stage,

growth stages that are critical when using Banvel® (dicamba), a Sandoz

product. .

' Producers believe that staging is complicated and difficult so it is

important to remember that producers have this preconceived, deeply ingrained

belief. When teaching crop staging it is important to emphasize that staging

small grain crops is simple, once a few skills are mastered.

Workshop participants were introduced to crop staging through the use

of a slide set. The first slide illustrated a plant with two leaves which was used

to discuss the purpose of the coleoptile and the physical differences between

the first and later leaves. When staging it is important to determine if the leaf

at the base of the plant is actually the first leaf when counting leaves on the

main tiller. If the first leaf is missing, which is often the case under field

conditions, improper herbicide application can occur if the plants have not

begun to tiller.

38

As use of the slide set progressed, staging became more complicated,

since the plants had three, then four leaves. Participants could easily count the

number of leaves so a plant was shown that had begun to tiller. At this point,

emphasis must be placed on the fact that you only count leaves on the main

tiller, not the leaves on secondary and tertiary tillers. This is done by finding

the prophyll of each tiller. The prophyll, like the coleoptile protects the

emerging growing point. Once the prophyll is located, the participants should

remove any secondary and tertiary tiller tissue enclosed within the prophyll.

The remaining plant parts emanate from the main tiller and can be easily

counted.

When plant development reaches the five- to six-leaf stage, the node

elongates, and the seed head emerges. Most of the participants did not realize

that seed head development began at such an early stage. This stage of

development is critical for herbicide application. Later applications of herbicides

often effect the developing seed head and significantly reduce yields.

At this point in the workshop, participants were given the pamphlet

(Figure 4) and the Zadok scale was explained. The Zadok scale permits

whoever is staging their crop to record a precise description of plant

development at the time of herbicide application. When using the Zadok scale,

only the highest number is used when determining which herbicide to apply.

X

39

Participants were especially appreciative of the herbicide list on the back page

of the pamphlet which provided the proper crop stage of application for each

herbicide listed.

Plants were given to each participant. Normally, plants in the three- to

four- and the five- to six-leaf stages were used. This limited the amount of

plant material needed but was sufficient to demonstrate plant development.

The first plant, in the three- to four-leaf stage, was used to familiarize

participants with both counting leaves, and to observe the rounded tip of the

first leaf. Later leaves have a more pointed leaf tip^

The second plant, in the five- to six-leaf stage, was used to demonstrate

tillering, and node elongation. Plants in this stage usually have one to three

tillers and at least one node. Once the main tiller was located and the number

of leaves counted, the number of nodes was determined. Participants would

run their fingers along the main tiller feeling for "bumps" vyhich are the nodes

or joints. After locating nodes, the main tiller was cut longitudinally with a

razor bladerto facilitate location of the developing seed head. Often what felt

like one node was actually two since node separation had already taken place.

A node wasn't counted as a separate node until it was I cm or more above the

node below it.

The staging workshops were popular. Participants repeatedly stated they

had been trying unsuccessfully to stage plants for many years. They were

especially impressed that small grain head development was easily observed at

)

40

the five- to six-leaf stage.' This observation made it easy to teach the

relationship between improper herbicide application timing and crop injury. The

success and popularity of the staging workshops indicates the need for more

"hands on" workshops related to weed science.

41

A WEED SURVEY OF PEPPERMINT FIELDS IN THE FLATHEAD VALLEY,MONTANA

»

Introduction-

Peppermint has been grown in the Flathead valley of Montana since

1968. The oil is sold primarily for human consumption, so the crop must be

grown weed-free for flavor and color purposes. Few herbicides are registered

for weed control in peppermint. Although numerous cultural and chemical

control practices exist, weeds continue to be a problem for the peppermint

producer.

A weed survey, was conducted in 34 out of a total of 58 mint fields

during June of 1991. The purpose of this survey was to identify the weed

species in peppermint fields, to determine which weed control practices were

being used, and to determine the effectiveness of the various control practices.

In addition, producers completed a questionnaire for each field to provide

background information on the weed control practices used including cultural

practices, herbicide use, and crop rotations in the cropping seasons before and

after peppermint production. Producers were asked to identify the weed they

felt most troublesome in each peppermint field.

CHAPTER 4

42


Thirty-four of the .58 peppermint fields listed with the Western Montana

Mint Growers Association of Kalispell, MT were surveyed in June, 1991.

Peppermint is commonly .grown in a field for five to six years, so an effort was

made to select fields of each age in an attempt to record weed species shift

over time. Permission to survey fields was obtained from each producer. The

survey method used was developed by Thomas (1985). Twenty locations were

sampled in each field. The locations were selected using an "M" pattern

(Figure 3). At each location, weed species per m2 were counted in a wire

frame, using common names accepted by the Weed Science Society of

America. Unknown species were identified by Todd Keener, Research

Specialist II, Northwestern Agricultural Research Center, Kalispell, MT.

Figure 3. The "M" surveying pattern used ensured each field was uniformly and randomly sampled.

43

Weed populations were quantified using the seven measurements

described below:

Frequency measured the number of fields in which a given species

occurred at least once. Frequency is expressed as a percentage of the fields

containing the weed out of 34 surveyed fields. The equation used was:

■ . nE yi

Fk = — X 100n.

Where Fk = frequency value for species kYi = presence ( I) or abscence (0) of species k in field i n = number of fields surveyed

Field Uniformity measured the number of individual sampling locations

in which a species occurred. It was expressed as a percentage of the total

number of sampling locations for all fields (34 fields x 20 sampling locations).

Field uniformity is a valuable measurement in that it measures the distribution

of a weed species in all of the fields surveyed. High uniformity indicates that

a weed species occurs frequently throughout all of the fields surveyed. The

equation was:

4 4

n 20

E E= T oHl x» x 100

where Uk = field uniformity value for species kX ij = presence ( I) or absence (0) of species in quadrant j

in a given field

Occurrence Field Uniformity measures the number of sampling

locations in which a species occurred in a given field. It was expressed as a

percentage of the total number of sampling locations of those fields where

the species occurred. Occurrence field uniformity measures the distribution

of a weed species throughout those fields where that species occurs. A

high occurrence field uniformity indicates that a weed species occurs

frequently throughout the field where that weed species was found. This

value is especially useful for farmers who do not have the weed so they can

provide the management needed to prevent its introduction into a given

field. The equation used was:

E EUAk 20 (n -a ) Xij X 100

where UAk = occurrence field uniformity value for species ka = the number of fields in which the species is absent

45

Mean Field Density was calculated by totalling each field density for a

species and dividing by the total number of fields surveyed. Mean field density

measures the average density of a weed species throughout all of the fields

surveyed. The equation used to calculate density (Di) was:

20

vyhere Di = density (expressed as number/m2) value of species in field i

Zj = nurpber of plants in quadrant j (a quadrant is 1.0 hn2)

Mean field density (MFDk) was calculated by:

34

EMFDk = — Di K n ‘

Mean Occurrence Field Density was calculated by totalling each field

density for a given species and dividing only by those fields where the species

occurred. Mean occurrence field density measures the average density of a

weed species in only those fields where it occurred. The equation used was:

EMOFDk = Dik n -a '

where a = the number of fields in which a species is absent

46

The Relative Abundance (RA) is a composite value of the frequency,

occurrence, and density for a species. Relative abundance has no units and is

used to. compare the relative abundance of one species to another. For

example, a species with an RA of 36 would be twice as abundant as a species

with an RA of 18.

The equation to calculate RA was:

RA = RFk + RUk + RDk

where

RFk frequency of species k sum of frequencies for all species

X 100

RUt field uniformity of species k sum of uniformities for all species

x 100

RDk mean field density of species k 100 sum of MFD for all species

A questionnaire was completed for each field surveyed to obtain

background information on the field and weed control practices, used.

Information collected included ownership, location of the field (section,

township and range), soil type, row spacing, variety, expected yield, perception

47

of major weed problem(s), crop rotations before and after mint production,

seedbed preparation, cultural practices before, during and after peppermint

production, herbicides used, fertilizer rates, and irrigation dates and amounts.


The questionnaire filled out by each producer interviewed, included 10

questions about their farm, the problems encountered in peppermint production,

the producers perception of the worst weed problem, crop rotations used,

seedbed preparation, and cultural practices used during and after peppermint

production. A total of 19 peppermint producers were interviewed, but only 16

producers had fields surveyed. Producers ranged in years of production from

first-year production to one farmer who had produced peppermint for 23 years

(Figure 4).

7 —

Years of Production

Figure 4. The number of years farmers have been in peppermint production.

'48

Of the 19 farmers interviewed, 17 liked growing peppermint. Two

producers said they weren't sure if they liked growing peppermint, that "time

would tell".

Producers were asked to rank the three most important production

problems they faced in order of importance. The first problem listed, by each

producer was given a score of three, the second a score of two and the third

a score of one. The scores were totalled and ranked in order of importance

(Table 7).

Table 7. The thirteen major productionproblems as perceived by peppermint producers in the Flathead valley.

Problem Cumulative Score

Weeds 41

Insects 27

Weather 17

Water 5

Labor and management 4

Spray timing. 3

Poor stand establishment 3

Diseases 2

Cultural practices I

Nematodes I

Money I

Lack of good chemicals I

Mint processing I

Weeds were the most important problem followed by insects. Weather was

third, and problems 4 through 13 were shared by very few of the growers.

Producers were then asked to list the two weeds they felt were most

troublesome. The most troublesome weed listed by each producer was given

a score of two, the second most troublesome weed listed by each producer

was given a score of one. The scores were totalled and ranked in order ofI

importance (Table 8). Two of the seventeen producers reported they had no

"troublesome" weeds. They felt their control practices were working

adequately, or that the "most troublesome" weed did not reduce oil yield.

It is worth noting that all of the "most troublesome" weeds are quite

visible in a field. Short-statured plants such as Kentucky bluegrass (Poa

pratensis L.) and scouringrush (Equ/setum hyema/e L ) ,vwhich are less visible

are not usually perceived as troublesome, even though they were often found

in very high densities. Common groundsel and catchweed bedstraw were the

number one and number two weeds, respectively, listed by producers.

Producers were asked to list their crop rotations for a three-year period

before peppermint was planted and what crops they planned to plant after

peppermint was taken out of production. The results show clearly that the pre-

and post-peppermint rotations vary greatly (Table 9).

50

Table 8. The thirteen weed species perceived to be the most troublesome by peppermint producers in the Flathead valley.

Number Weed Species Latin NameCumulative

Score

I common groundsel Senecio vulgaris L. 12

2 catchweed bedstraw Gaiium aparine L. . 10

3 Canada thistle Cirsium arvense L. 7

4 annual and perennial grasses

Agropyron and Poa spp. 6

5 wild oat Avena fatua L. 5

6 wild buckwheat Polygonum convolvulus L. 5

7 pigweed spp. Amaranthus spp. 3

8 Russian thistle Salsola iberica S&P 2

9 field bindweed Convolvulus arvensis L. 2

10 common mullein Verbascum thapsus L. 2

11 blue mustard Chorispora tene/fa (Pall.) DC. 2

12 pansy Viola pedatifida G. Don. 2

13 henbit Lamium amplexicaule L. I

\

51

Producers were then asked to describe the cultural practices used in each

field during peppermint production (Table 10). Similar answers were grouped

together and summed. Producers implemented cultural practices, if used, after

the peppermint rows began to fill in, either in late fall or early spring, after the

second year of production, five of the producers used a combination of the

cultural practices listed, depending on the age of the stand. The older the

stand, the more aggressive was the treatment.

The final question asked was: how was your seedbed prepared before

planting peppermint root pieces? Similar answers were grouped and summed

(Table 11). The results indicate that most of the growers thoroughly prepare

their seedbeds prior to planting.

After each peppermint producer was interviewed, fields were surveyed

as described previously. Forty weed species were found in 34 peppermint

fields in 1991 with an average of 7 weed species per field and a density of 6.6

weeds per m2. The heaviest infestation recorded in an individual field was 51

weeds per m2. The lowest infestation recorded in an individual field was 2.9

weed species per m2.

All producers used herbicides. All but one producer hand-rogued his

fields at least once during the growing season. Most hand-roguing occurred

after the peppermint was too tall to get spray equipment into the field without

sustaining crop damage from wheels.

52

The five most common weed species occurring in all 34 peppermint fields

were, in order of frequency, wild oat, quackgrass, common groundsel,

catchweed bedstraw and Canada thistle (Table 12). Wild oat and common

groundsel each occurred with a frequency of 55.9% . Wild oat had a field

uniformity of 18.8% and common groundsel had a field uniformity of 10.1% .

Wild oat and common groundsel occurred in 42.7% and 23.0% of all sampling

locations, respectively.

The five most common weed species occurring in the nine first year

peppermint fields surveyed were, in order of frequency, wild oat, barley,

quackgrass, Canada thistle, and wheat (Table 13). Wild oat, barley and Canada

thistle each occurred with a frequency of 67.0% , 78.0% , and 67.0% ,

respectively. Wild oat had a field uniformity of 36.7% , barley had a field

uniformity of 19.4% , and Canada thistle had a field uniformity of 13.3%. Wild

oat, barley, and Canada thistle each had ah occurrence field uniformity of

61.2% , 48 .5% , and 22.2% respectively, in peppermint fields in their first year

of production.

In the eight second year peppermint fields surveyed, wild oat, catchweed

bedstraw, Russian thistle, common groundsel, and meadow salsify were the

most frequently occurring weed species (Table 14). Wild oat and catchweed

bedstraw each occurred with a frequency of 75.0% . Wild oat had a field

uniformity of 21.9% , catchweed bedstraw had a field uniformity of 13.7%.

Table 9. Crop rotations before and after peppermint production.

Years. Before Peppermint Production_________ Years in ______ Years After Peppermint ProductionRespondent 5 4 3 2 I Peppermint I 2 3 4 5

I Barley Barley Barley Fallow 7 SmallGrains^

SmallGrains

SmallGrains

SmallGrains

SmallGrains

2 Barley WinterWheat

Alfalfa Alfalfa WinterWheat

5 SmallGrains

SmallGrains

Mint

3 Barley Alfalfa Alfalfa Alfalfa Alfalfa 6 Alfalfa Alfalfa Alfalfa Alfalfa Barley

4 Barley Barley Alfalfa Alfalfa Alfalfa 5-6 SmallGrains

SmallGrains

SmallGrains

Alfalfa Alfalfa

5 WinterWheat

Fallow Barley 4-5 Barley Barley Barley Barley Mint

6 Barley Barley Barley 5-6 Barley Barley Barley Barley

7 Pasture Pasture Barley Barley Barley 7 Unknown

8 SmallGrains

SmallGrains

SmallGrains

5-6 SmallGrains

SmalliGrains

SmallGrains

SmallGrains

Fallow;

9 Fallow WinterWheat

Barley 5-6 Barley Barley Legume or Wheat

Mint

10 SpringWheat

SpringWheat

SpringWheat

7 WinterWheat

Barley Fallow Mint

11 Barley SpringWheat

Fallow 5-6 SmallGrains

SmallGrains

SmallGrains

SmallGrains

12 Barley Barley 5 Barley Barley Mint

(Continued)

Table 9. Crop rotations before and after peppermint production.(Continued)

Years Before Peooermint Production Years in Years After Peooermint ProductionRespondent 5 4 3 2 I Peppermint I 2 " 3 4 5

13 Alfalfa Alfalfa A lfa lfa . 15 Mint

14 SpringWheat

Lentils SpringWheat

4-5 Alfalfa Alfalfa Alfalfa Alfalfa Alfalfa

15 SpringWheat

SpringWheat

SpringWheat

6-8 SmallGrains

SmallGrains

SmallGrains

16 Barley Barley Barley 6 Alfalfa Alfalfa Alfalfa Alfalfa

17 Barley Barley Barley 6 SpringWheat

SpringWheat

SpringWheat

55

Table 10. Cultural practices used during peppermint production.

Cultural Practices Used During Peppermint Production

Number of Producers

Disced lightly 9

No cultural practices used 5

Harrowing or field cultivation 3

Fall corrugation 3

Shallow moldboard plowing I

Table 11 . Seedbed preparation practices used before planting peppermint.

Seedbed Preparation PracticeNumber of Producers

Plow, cultivate, pack, plant, harrow, cultipack 11

Chisel plow, disc, harrow 3

Plow, pack, spray with glyphosate, plant, pack

2

Burn, cultivate, plant, harrow 2

Plant into fallow, pack I

Disc stubble, plant I

Field uniformity of wild oat and catchweed bedstraw was 54.7% , and 34.3%

respectively, in peppermint fields in their second year of production.

The five most common weed species in five third year peppermint fields

were, in order of frequency, quackgrass, wild oat, Canada thistle, meadow

salsify, and catchweed bedstraw (Table 15). Quackgrass, Canada thistle, and

56

meadow salsify each occurred with a frequency of 60.0% , however, the

relative abundance ratings varied greatly. Even though each specie had the

same frequency of occurrence, the densities varied greatly as indicated by field

uniformities of 3.2% , 2.0% , and 1.4%, respectively.

The most abundant five weed species in seven fourth year peppermint

fields were, in order of frequency, common groundsel, wild oat, quackgrass,

meadow salsify, and catchweed bedstraw (Table 16). Common groundsel and

meadow salsify each occurred with a frequency of 71.4% , but meadow salsify

had a relative abundance approximately one-half that of common groundsel.

The field uniformity for common groundsel was 15.0% while meadow salsify

only had a field uniformity of 5.7% .

In five peppermint fields that were six years old or older, common->

groundsel, meadow salsify, dandelion, Kentucky bluegrass and prostrate

pigweed, were the most frequent weeds found (Table 17). Common groundselI

and meadow salsify each had a frequency of occurrence of 100.0% and

80.0% , respectively. Common groundsel was found in all sampling locations.

Four herbicides were used in the fields surveyed in 1991 (Table 18). The

most frequently used herbicides were, in order, Sinbar (terbacil), Gramoxone

(pardquat), Basagran (bentazon), and Stinger (clopyralid). All peppermint fields

were irrigated frequently to maintain soil moisture in the top 14 cm of soil. Soil

types where peppermint was grown ranged from sandy loams to heavy clay

57

loams. All fields were planted to the same variety, 'Black Mitcham', originally

planted in rows 49-53 cm apart.

Plants eventually grew and filled in between plants and rows so a solid

stand was obtained by the fourth year of production. Solid stands required

mechanical renovation to disrupt rhizomes to provide rejuvenation. Expected

yields ranged from 50 pounds of oil per acre from first year peppermint fields,

to 120 pounds of oil per acre from two to three year old stands.

58

CHAPTER 5

SUMMARY

Since many agricultural producers in Montana have difficulty identifying

weed seedlings and staging small grains for herbicide application, portable

workshops were developed to teach these concepts. The workshops were

highly portable using a standard pick-up truck and contained live plant material

that allowed for hands-on activities that often help adults learn. Many

participants expressed that they felt they had learned a great deal from these

workshops and would feel more confident identifying weed seedlings and

staging small grain crops in their own fields.

Peppermint producers in the Flathead valley of Montana were interested

in identifying what weed species were occurring in peppermint fields

throughout the valley. Producers were asked to fill out a simple survey about

their production practices. After the survey was completed, 34 of the 58

peppermint fields were surveyed to determine weed species and density per m2.

t

Table 12. Frequency, occurrence, density, and relative abundance of 40 weed species common to peppermintfields surveyed in 1991.

Plant Species FrequencyField

Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (— -NUMBER/m2 )

Wild Oat (Avena fatua L.)

55:9 18.8 42.7 2.4 4.4 47.5

Quackgrass (Agropyron repens L.)

44.1 11.9 21.3 0.5 1.2 28.3

Common Groundsel (Senecio vulgaris L.)

55.9 10.1 23.0 0.5 0.9 29.3 „LO

Catchweed Bedstraw [Galium aparine L.)

47.1 8.1 15.3 0.4 0.9 22.1

Dandelion(Taraxacum officinale W.)

35.3 6.5 10.0 0.1 0.3 19.9

Meadow Salsify (Tragopogonpratensis L.)

50.0 6.0 12.1 0.1 0.2 18.9

Canada Thistle (Cirsium arvense L.)

44.1 6.5 11.6 0.4 1.0 18.3

(Continued)

Table 12. Frequency, occurrence, density, and relative abundance of 40 weed species common to peppermintfields surveyed in 1991.(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField.

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (-----NUMBER/m2-— )

Barley(Hordeum vulgare L.)

35.3 6.8 10.5 0.2 0.5 16.7

Wild Buckwheat (Polygonum convolvulus L.)

32.4 4.1 6.1 0.1 0.3 11.5

Russian Thistle (Salsola Iberica S&P)

23.5 4.1 5.4 0.4 1.5 CO CO

09

Prostrate Knotweed (Polygonum aviculare L.)

26.5 3.7 5.0 0.1 0.3 9.8

Henbit(Lamium amp/exicaule L.)

8.8 0.6 0.6 0.01 0.1 9.6

Scouringrush (Equisetum hyemale L.)

20.6 2.2 2.8 0.1 0.4 6.4

Prickly Lettuce (Lactuca scariola L.)

23.5 1.3 1.7 0.1 0.3 5.5

(Continued)

Table 12. Frequency, occurrence, density, and relative abundance of 40 weed species common to peppermintfields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) . (%) (-----NUMBER/m2-— ) "

Kentucky Bluegrass (Poa pratensis L.)

14.7 2.1 2.4 0.2 1.5 5.3

Wheat[Triticutn aestivum L.)

14.7 1.9 2.2 0.02 0.2 5.0

Field Bindweed (Convolvulus arvensis L.)

17.6 1.5 1.8 0.1 0.5 4.8 m

Green Foxtail (Setaria viridis L.)

5.9 2.4 2.5 0.2 3:2:

4.3

IVIouse ear Chickweed (Stellarla media (L ) Vi 11.)

14.7 1.2 1.4 0.05 0.4 3.9

Blue-eyed Mary (Collinsia parviflora LjndI.)

11.8 1.3 1.5 0.1 0 .6 3.7

Blue Mustard(ChorispOra tenella (Pall.) DC.)

14.7 1.0 1.2 0.03 0.2 3.6

(Continued)


Plant Species Frequency

(%)

FieldUniformity

(%)

OccurrenceField

Uniformity

(%)

MeanMean OccurrenceField Field

Density Density

(-— NUMBER/m2-— )

RelativeAbundance

Prostrate Pigweed (Amaranthus blitoides L.)

8.8 1.3 1.5 0.3 3.7 3.3

Small Seeded Falseflax (Camelina microcarpa Andrz. ex DC.)

11.8 0.6 0.7 0.01 0.05 2.6

CDNight Flowering Catchfly

(Silene noctiftora L.)8.8 0.6 0.6 0:04 0.4 . 2.1 1X3

Field Pennycress (Thlaspi arvense L:)

8.8 0.5 0.6 0.01 0.1 2.0

Pineapple Weed(Matricaria matricarioides (Less.) Porter

2.9 1.0 1.1 0.05 1.8 1.9

Wild Mustard(Brassica kaber (DC) Wheeler)

5.9 0.6 0.6 0.01 0.1 1.6

Kochia(Kochia scoparia (L.) Schrad)

5.9 0.3 6.3 0.01 0.1 . 1.6

(Continued)

Table 12. Frequency, occurrence, density, and relative abundance of 40 weed species common to peppermintfields surveyed in 199 1 .(Continued)


(%)

FieldUniformity

(%)

OccurrenceField

Uniformity

(%)

MeanMgan OccurrenceField Field

Density Density

(-----NUMBER/m2-— )

Relative , Abundance

Alfalfa '(Medicago sativa L.)

5.9 0.4 . 0.5 <0.01 0.1 1.5

Corn Gromwell (Lithospermum arvense L.)

2.9 0.7 0.8 0.01 0.4 1.4

Pinnate Tansy Mustard (Descurainiapinnata (Walt.) Britt)

5.9 0.3 0.3 <0.01 0.05 1-3 mCO

Cowcockle(Vaccaria pyrami data M.)

5.9 0.3 0.3 <0.01 0.05 1.3

Tumble Mustard (Sisymbrium a/tissimum L.)

5.9 0.3 0.3 <0.01 0.1 1.3

Pansy(Viola pedatifida G. Don.)

5.9 0.3 0.3 <0.01 0.05 1.3

Common Mullein (Verbascum thapsus L.)

2.9 0.3 0.3 <0.01 0.1 0.9

(Continued)



(%)

FieldUniformity

(%)

OccurrenceField

Uniformity

(%)


Density Density

(—,.NUMBER/m2-----)

RelativeAbundance

Common Lambsquarters (Chenopodium album L.)

2.9 0.1 0.2 <0.01 0.5 0*6

Broadleaf Plantain (Plantago major L.)

2.9 0.1 0.2 <0.01 0.1 0.6

Cone Catchfly {Si/ene conoidea L.)

2.9 0.1 0.2 <0.01 0.05 0 .6 2

Cheatgrass (Downy Brome) [Bromus tectorum L.)

2.9 0.1 0.2 <0.01 0.05 0.6

Yellow Toadflax (Unaria vulgaris Mill.)

2.9 0.1 0.2 <0.01 0.05 0.6

Table 13. Frequency., occurrence, density, and relative abundance of 40 weed species common to first-yearpeppermint fields surveyed in 1991.


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (-— NUMBER/m2-— ).

Wild Oat ' (Avena fatua L.)

67.0 36.7 61.2 8.1 0.9 55.4


78.0 19.4 48.5 0.5 5.6 42.0


56.0 22.8 28.5 0.9 10.0 32.4 ^in

Canada Thistle (Cirsium arvense L.j

67.0 13.3 22.2 1.0 11.1 26.0

Wheat(Triticum aestivum L.)

44.0 13.9 13.9 0.1 1.1 19.6


44.0 10.0 10.0 0.3 0.3 15.8


44.0 8.9 8.9 0.3 3.3 14.8

(Continued)

Table 13. Frequency, occurrence, density, and relative abundance of 40 weed species common to first-yearpeppermint fields surveyed in 199 1 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (-— NUMBER/m2-— )


33.0 8.9 7.4 0.1 1.1 13.3

Catchweed Bedstraw (Galium aparine L.)

33.0 8.3 6.9 0.4 4.4 12.1

Russian Thistle (Salsola iberica S&P)

33.0 6.7 5.6 1.1 12.2 p vi99


11.0 7.8 4.9 '0 .5 5.6 7.9

Mouse-ear Chickweed (Stei/aria media (L.) Vill.)

33.0 3.3 2.8 0.2 2.2 7.6


22.0 4.4 3.1 0.1 1.1 6.8

Wild Mustard(Brassica kaber (DC) Wheeler)

22.0 2.2 1.6 0.02 0.2 5.0

(Continued)

Table 13. Frequency, occurrence, density, and relative abundance of 40 weed species common to first-yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) ' (%) (%) (-----NUMBER/m2-— )

Pineapple Weed(Matricaria matricarioides (Less.) Porter

11.0 3.9 2.4 0.2 2.2 4.6


22.0 1.1 0.8 0.02 0.2 4.0


11.0 2.8 1.8 0.01 0.07 3.8 ^

Corn Gromwell (Lithospermum arvense L.)

11.0 2.8 1.8 0.04 0.4 3.8

Alfalfa[Medicago sativa L.)

11.0 1.1 0.7 0.1 0.1 2.4

Night Flowering Catchfly (Silepe noctiflora L.)

11.0 1.1 0.7 0.01 0.1 2.4

Henbit(Lamium amplexicaule L.)

11.6 0.6 0.4 6.01 0.07 2.0

(Continued)

Table 13. Frequency, occurrence, density, and relative abundance of 40 weed species common to first-yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (-— NUMBER/m2-----)

Kochia(Kochia scop aria (L.) Sch rad)

11.0 0.5 0.3 0.01 0.07 1.9

Pinnate Tansy Mustard [Descurainia pinnata (Walt.) Britt)

11.0 0.6 0.4 0.01 0.07 2.0


11.0 0.6 0.4 0.01 0.1 2.0 mOO

CowcoCkle(Vaccaria pyramidata M.)

11.0 0.6 0.4 0.01 0.1 2.0

Mean

Table 14. Frequency, occurrence, density, and relative abundance of 40 weed species common to second yearpeppermint fields surveyed in 1991.


Uniformity

OccurrenceField

Uniformity

MeanField

Density

OccurrenceField

DensityRelative

Abundance

(%) (%) (%) (——NUMBER/m2-----)


75.0 21.9 54.7 ' 0.7 0.1 74.5


75.0 13.7 34.3 1.1 0.1 50.7


62.5 8.1 13.5 0.1 0.01 27.9 m


50.0 5.0 6.2 0-07 0.01 17.4

Russian Thistle {Sa/so/a iberica S&P)

25.0 7.5 6.2 0.2 0.03 16.9

Canada Thistle (Cirsium arvenseL.)

50.0 3.7 4.6 0.2 0.03 14.7

Wild Buckwheat 37.5 4.4 4.4 0.1 0.01 13.7(Polygonum convolvulus L.)

(Continued)

Table 14. Frequency, occurrence, density, and relative abundance of 40 weed species common to second yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (-— NUMBER/m2-— )


37.5 4.4 4.4 0.1 0.01 13.7


37.5 3.1 3.1 0.08 0.01 11.2


25.0 3.7 3.1 0.05 0.01 i o . i _O

Field Bindweed (Con volvulus arvensis L.)

25.0 3.1 2.6 0.3 0.04 9.1

Prickly Lettuce (Lactuca scafiola L.)

37.5 1.9 1.9 0.06 0.01 CD b


25.0 1.2 1.0 0.01 <0.01 5.7


25.0 1.2 ,1.0 0.01 <0.01 5.7

(Continued)

Table 14. Frequency, occurrence, density, and relative abundance of 40 weed species common to second yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

Meanfield

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) „ (%) (-— NUMBER/m2 )


12.5 1.2 0.9 0.03 <0.01 3.8


12.5 1.2 0.8 0.2 0.03 3.7

Kochia(Kochia scoparia (L.) Schrdd

12.5 0.6 0.4 0.01 <0.01 2 -8 ^

Alfalfa(Medicago sativa L.)

12.5 0.6 0.4 0.01 <0.01 2.8

Common Lambsquarters (Chenopodium album L.)

12.5 0.6 0.4 0.01 <0 .01 2.8

Broadleaf Plantain (Plan tago major L.)

12.5 0.6 0.4 0.01 <0.01 2.8


12.5 0.6 0,4. 0.01 <0.01 2.8

(Continued)

Table 14. Frequency, occurrence, density, and relative abundance of 40 weed species common to second-yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) , (%) (-— NUMBER/m2—- )

Blue Mustard[Chorispora tene/la (Pall.) DC.)

12.5 0.6 0.4 0.01 <0.01 2.8

Cone Catchfly (Si/ene conoidea L.)

12.5 0.6 0.4 0.01 <0.01 2.8

IX)

Table 15. Frequency, occurrence, density, and relative abundance of 40 weed species common to third-yearpeppermint fields surveyed in 1991.


-(%)

FieldUniformity

(%)

OccurrenceField

Uniformity

(%)


Density Density

(-— N U M B E R / m )

RelativeAbundance

Quackgrass 60.0 3.2 8.0 0.9 0.2 56.7{Agropyron repens L.)

Wild Oat 40.0 2.2 3.7 0.2 0.04 32.8[Avena fatua L.)


60.0 2.0 5.0 0.7 0.14 39.1 ^CO


60.0 1.4 1.5r

0.1 0.02 23.6


40.0 1.2 2.0 ' 0.1 0.02 20.8


40.0 1.2 2.0 0.1 0.02 20.8


60.0 0.8 1.5 0.3 0.06 19.8

(Continued)

Table 15. Frequency, occurrence, density, and relative abundance of 40 weed species common to third-yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (— -NUMBER/m2-— )


40.0 0.6 1.0 0.03 <0.01 13.7

Henbit(Lamium amplexicaule L.)

40.0 0.6 1.0 0.04 <0.01 13.7

Blue-eyed Mary (Collinsia parviflora Lind I.)

20.0 0.8 1.0 0.08 O b 1 1 6 _

Field Pennycress (Th/aspiarvense L.)

20.0 0.6 0.8 0.03 <0.01 9.7


20.0 0.2. 0.3 0.01 <0.01 5.5


20.0 0.2 0.3 0.03 <0.01 5.5


20.0 0.2 0.3 0.01 <0.01 5.5

(Continued)

Table 15. Frequency, occurrence, density, and relative abundance of 40 weed species common to third-yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density.

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (—r-NUMBER/m2-— )

Mouse-ear Chickweed (SteUaria media (L.) Vill.)

20.0 0.2 0.3 0.01 <0.01 5.5

Prostrate Pigweed (Amaranthus biitoides L.)

20.0 0.2 0.3 0.01 <0.01 5.5

Cheatgrass (Downy Brome) (Bromus tectorum L.)

20.0 0.2 0.3 0.01 <0.01 5.5 _O l

Tumble Mustard (Sisymbrium altissimum L.)

20.0 0.2 0.3 0,01 <0.01 5.5

Table 16. Frequency, occurrence, density, and relative abundance of 40 weed species common to fourth-yearpeppermint fields surveyed in 1991.


(%)

FieldUniformity

(%)

OccurrenceField

Uniformity

(%)

. MeanMean OccurrenceField Field

Density Density

(-— NUMBERW-— )

RelativeAbundance


71.4 15.0 37.5 1.1 0.2 64.5


57.1 10.0 16.7 0.5 0.1 37.4

Meadow. Salsify (Tragopogonpratens/s L.)

71.4 . 5.7 14.3 0.06 0.01 32.2 _CTl


12.8 11.4 14.3 0.3 0.05 29.7


42.8 6.4 8.0 0.2 0.03 22.7

Scouringrush (Equisetum hyema/e L.)

28.6 5.0 5.0 0.2 0.03 15.8


42.8 2.1 2.6 0.05 o . o i 12.3

(Continued)

Table 16. Frequency, occurrence, density, and relative abundance of 40 weed species common to fourth-yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) _ (%) (%) (-— NUMBER/m2-— )


14.3 . 4.3 3.6 0.2 0.02 11.2

Dandelion[Taraxacum officinale W.)

28.6 2.1 2.1 0.06 0.01 9.5

Blue Mustard[Chorispora tenella (Pall.) DC.)

28.6 1.4 1.4 0.01 <0.01 CO bLL

Barley[Hordeum vulgare L.)

14.3 2.1 1.8 0.04 0.01 6.8

Prostrate Pigweed (Amaranthus blitoides L.)

14.3 2.1 1.8 0.14 0.02 6.8

Field Bindweed (Con volvulus arvensis L.)

14.3 1.4 1.2 0.05 0.01 5.3

Common Mullein (Verbascum thapsus L.)

14.3 1.4 1.2 0.01 <0.01 5.3

(Continued)

Table 16. Frequency, occurrence, density, and relative abundance of 40 weed species common to fourth-yearpeppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (-— NUMBER/m2- —)

Canada Thistle (Circsium arvense L.)

14.3 0.7 0 .6 0.06 0.01 3.8


14.3 0.7 0.6 0.01 <0.01 3.8

Russian Thistle (Salsola iberica S&P)

14.3 0.7 0.6 0.01 <0.01 3.8 ^CO

Field Pennycress (Thlaspi arvense L.)

14.3 0.7 0.6 0.01 <0.01 3.8

Pinnate Tansy Mustard (Descurainia pinnata (Walt.) Britt)

14.3 0.7 0.6 0.01 <0.01 3.8

Small Seeded Falseflax (Camelina microcarpa Andrz. ex

DC.)

14.3 0.7 0.6 0.01 <0.01 3.8

Mouse-ear Chickweed (Stel/aria media (L ) Vill.)

14.3 0.7 0.6 0.01 <0.01 3.8

Table 17. Frequency, occurrence, density, and relative abundance of 40 weed species common to six-year and .older peppermint fields surveyed in 1991.


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (—-NUMBER/m2-— )


100.0 30.0 150.0 1.2 0.2 77.7


80.0 18.0 90.0 0.3 0.1 49.2


60.0 16.0 40.0 0.3 0.1 CO CO

6Z


40.0 10.0 16.7 1.3 0.3 17.7


40.0 5.0 8.3 0.1 0.03 11.3


40.0 4.0 6.7 0.1 0.02 10.0

Blue-eyed Mary (Collinsia parviflora Li nd I.)

40.0 4.0 6.7 0.4 0.1 10.0

(Continued)

Table 17. Frequency, occurrence, density, and relative abundance of 40 weed species common to six year andolder peppermint fields surveyed in 1991 .(Continued)

?Plant Species Frequency

FieldUniformity

OccurrenceField

Uniformity

MeanField

Density.

MeanOccurrence

FieldDensity

RelativeAbundance

(%) ' (%) (%) (-— NUMBER/m2-— ).

Blue Mustard(Chorispora tenella (Pall.) DC.)

40.0 4.0 6.7 0.2 0.04 10.0

Russian Thistle {Salsola iberica S&P)

40.0 3.0 5.0 0.1 0.02 8.8

Prostrate Pigweed {Amaranthus b/itoides L.)

20.0 5.0 6.3 2.0 0.4 80C

N

CO


20.0 5.0 6.3 0.01 0.00 8.2


40.0 2.0 3.3 0.2 0.04 7.4


20.0 2.0 2.5 0.02 0.00 4.7

Wild Oat (A vena fatua L.)

20.0 2.0 2.5 0.05 0.01 4.7

(Continued)

Table 17. Frequency, occurrence, density, and relative abundance of 40 weed species common to six-year andolder peppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

Mean Field -

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) (— -NUMBER/m2-— )


20.0 2.0 2.5 0.04 0.01 4.7


20.0 1.0 1.3 0.03 0.01 3.6

Wheat(Triticum aestivum L.)

20.0 1.0 1.3 0.01 <0.01 3.6 ooI— 1


20.0 1.0 1.3 0.1 0.02 3.6


20.0 1.0 1.3 o . o i <0.01 3.6

Night Flowering Catchfly (Silene noctif/ora L.)

20.0 1.0 1.3 0.05 0.01 3.6 .

Mouse-ear Chickweed (Stallaria media (L ) Vill.)-

20.0 1.0 1.3 0.05 0.01 3.6

(Continued)

Table 17. Frequency, occurrence, density, and relative abundance of 40 weed species common to six-year andolder peppermint fields surveyed in 1991 .(Continued)


Uniformity

OccurrenceField

Uniformity

MeanField

Density

MeanOccurrence

FieldDensity

RelativeAbundance

(%) (%) (%) . ( - —NUMBER/m2-— )

Cheatgrass (Downy Brome) (Bromus tectorum L.)

20.0 1.0 1.3 0.01 <0.01 3.6

Tumble Mustard (Sisymbrium altissimum L.)

20.0 1.0 1.3 0.02 <0.01 3.6

Yellow Toadflax (Linaria vulgaris Mill.)

20.0 1.0 1.3 0.01 <0.01 3.6 oono

Pansy(Viola pedatifida G. Don.)

20.0 1.0 1.3 0.03 <0.01 3.6

83

Table 18. Field age, weed density, number of species, and weed control practices used in 34 peppermint fields surveyed in 1991.

FieldNumber

FieldAge

YearsWeeds/

20m2

Number of Weed

Species HerbicidesApplication

Rate

I 2 59 7 Sinbar I Ib/A

2 I 82 4 Sinbar + Gramoxone

Extra Stinger Basagran

I Ib/A + 1-1.5 pt/A

0.3 pt/A 1-2 pt/A

3 3 88 4 Same as field #2


5 4 140 11 Sinbar + Paraquat

Basagran Stinger

2/3 Ib/A + I qt/A I pt/A

2/3 pt/A


7 2 165 10 SinbarStingerBasagran

6.8 Ib/A 0.5 oz/A

I pt/A

8 I 176 13 SinbarBasagranStinger

I Ib/ANot Available

I pt/A

9 2 47 8 SinbarGramoxoneBasagrahStinger

0.7 Ib/A 2 oz/A

Not Available I pt/A

(Continued)

84

Table 18. Field age, weed density, number of species, and weed controlpractices used in 34 peppermint fields surveyed in 1991 .(Continued)

FieldNumber

FieldAge

YearsWeeds/

20m2

Number of Weed


Rate

' 10 2 52 10 Sinbar 0.25 Ib/AGramoxone 8-12 oz/AStinger I pt/A

11 3 32 53 Same as field #10


13 I 111 8 Same as field #10

14 I 276 5 Sinbar + I Ib/A +• „ Gramoxone I pt/A

Stinger 0.5-0.7 pt/ASinbar + I Ib/A

Basagran I pt/A



17 3 79 7 Sinbar 0.25-0.5 Ib/AGramoxone I qt/ABasagran 2 pt/AStinger 0.25-0 .5 pt/A


19 I 80 5 Same as.field #17

20 4 75 . 6 Sinbar I Ib/AParaquat I pt/ABasagran 2 pt/A .Stinger 0.25-0.5 pt/A

21 2 113 9 Same as field #20


(Continued)

85

Table 18. Field age, weed density, number of species, and weed controlpractices used in 34 peppermint fields surveyed in 1991 .(Continued)

FieldNumber

FieldAge

YearsWeeds/

20m2

Number of Weed


Rate

23 4 33 6 SinbarGramoxoneBasagranStinger

I lta/A< 0.25 pt/A

< 2 pt/A I pt/A

24 3 31 10 Same as field #23

25 7 32 6 SinbarGramoxoneBasagranStinger

• < I Ib/A < I pt/A

Not Available Not Available

26 4 65 6 Same as field #25*


28 2 8 I SinbarBasagranStinger

0.5-1 Ib/A Not Available Not Available

29 8 107 11 Same as field #28

30 4 25 4 Sinbar I Ib/A

31 6 279 2 Sinbar I Ib/A

32 4 11 5 SinbarParaquatStingerBasagran

0.25 Ib/A 8-12 oz/A < I qt/A

2 pt/A

33 15 177 12 Same as field #32

34 I 300 6 SinbarBasagran

I Ib/A I qt/A

86

REFERENCES CITED

87

References Cited

Bowran, D.G. 1986. Tolerance of cereal crops to herbicides. Journal of Agriculture in Western Australia 27:14-17.

Brandt, W .H., M.L. Lacy and C.E. Horner. 1984. Distribution of VerticilUum in stems of Resistant and Susceptible Species of Mint. Phytopathology 74: 587-591.

Bubel, N. 1985. Mint Conditions. Horticulture 63:58-61.

' Clark, R.J. and R. C. Menary. 1980. Environmental Effects on Peppermint [Mentha piperita L.). I. Effect of Daylength, Photon Flux Density, Night Temperature and Day Temperature on the Yield and Composition of Peppermint Oil. Australian Journal of Plant Physiology 7:685-92.

Cramer, G.L. and O.C. Burnside. 1980. Weeds - Identification and Control. Farm, Ranch and Home Quarterly Institute of Agriculture and Natural Resources. University of Nebraska - Lincoln.

Davidson, D.J. and P.M. Chevalier. 1990. Preanthesis tiller mortality in spring wheat. Crop Science 30:832-836.

DeAngeIis, J.D., A.B. Marin, R.E. Berry, and G.W. Krantz. 1983. Effects of Spider Mite (Acari: Tetranychidae) Injury on Essential Oil Metabolism in Peppermint. Environmental Entomology 12: 522-527.

Farrell, K.T. Spices, Condiments and Seasonings. 1985. The AVI Publishing Co., Inc. Westport, CT. 143-146 pp.

Hollingsworth, C.S., and R.E. Berry. 1982. Twospotted Spider Mite (Acari: Tetranychidae) in Peppermint: Population Dynamics and Influence of Cultural Practices. Environmental Entomology 11:1280-1284.

Jenkins, W.R. and D.P. Taylor. 1967. Plant Nematoloov. Reinhold Publishing Company, New York. 270 p.

Kimpinski, J. and R.A. Dunn. 1984. Effect of Low Temperatures in the Field and laboratory on Survival of Pratylenchus penetrans. Plant Disease 69:526-527.

(Continued)

88

References Cited, Continued

Kirby, E.J.M. 1977. The growth of the shoot apex and the apical dome of barley during ear initiation. Annals of Botany 4 1 :1297-1308.

Kirby, E.J.M., and M. Appleyard. 1986. Cereal development guide. Arable Unit, National Agricultural Centre, Stonelight, Kenilworth, Warwickshire, England. 1-95 pp.

Landes, A., and J.R. Porter. 1990. Development of the inflorescence in wild oats. Annals of Botany 66:41-50.

Leonard, David. 1991. The Nematode. Horticulture. 69: 66-73.

Lindquist, J.L., P.K. Fay, and J.E. Nelson. 1989. Teaching Weed Identification at Twenty U.S. Universities. Weed Technology 3:186-188.

Macleod, D. A Book of Herbs. 1968. Butler and Tanner, Ltd. Frome and London. 111-113 pp.

Martin, D.A., S.D. Miller, and H.P. Alley. 1990. Spring wheat response to herbicides applied at three growth stages. Agronomy Journal 82:95-97.

Nelson, J.E.. 1986. The Broadleaf Seedling Key. Montana State University Extension Bulletin #7.

Nelson, J.E, Kephart, K.D., Bauer, A., and Connor, J.F. 1990. Growth staging of wheat, barley, and wild oat: A strategic step to timing of fieldoperations. Montana State University Extension Publication.

Nerson, H., M. Sibony, and M.J. Pinthus. 1980. A scale for the assessment of the developmental states of the wheat (Triticum aestivum L.) spike. Annals of Botany 45:203-204.

Nicholls, P.B. 1974. Interrelationship between meristematic regions \of developing inflorescences of four cereal species. Annals of Botany 38:827-837.

Perry, M .W ., D.G. Bowran> and G. Brown. 1986. Using the Zadoks growth scale. Journal of Agriculture in Western Australia 27:11-13.

(Continued)

r

89

References Cited, Continued

Poinar, G.O. 1983. The Natural History of Nematodes. Prentice Hall, Inc. 323 p.

Rawson, H.M., and C.M. Donald. 1969. The Absorption and distribution of nitrogen after floret initiation in wheat. Australian Journal of Agricultural Research 20:799-808.

Sanders, L. 1987. Skills for diagnosing crop problems can increase yields and profits. Better Crops with Plant Food 71:6-9.

Stucky, J.M. 1984. Comparison of Two Methods of Identifying Weed Seedlings. Weed Science 32:598-602.

Thomas, A.G. 1985. Weed Survey System Used in Saskatchewan for Cereal and Oil Crops. Weed Science 33:34-43.

Tottman, D.R. 1977. The identification of growth stages in winter wheat with reference to the application of growth-regulator herbicides. Annals of Applied Biology 87:213-224. '

Tottman, D.R, 1987. The decimal code for the growth stages of cereals, with illustrations. Annals of Applied Biology 110:441-454.

West, C.P., D.W. Walker, R.K. Bacon, D.E. Longer and K.E. Turner. 1991. Phenological analysis of forage yield and quality in winter wheat. Agronomy Journal 83:217-224.

Williams, K. Eating Wild Plants. 1977. Mountain Press Publishing Co. Missoula, MT. 9-13 pp.

Zadoks, J.C., T.T. Chang, and C.F. Konzak. 1974. A decimal code for the growth stages of cereals. Weed Research 14:415-421.

90

APPENDIX

91

APPENDIX

A Teaching Guide for Weed Seedling Identification

Slide I : Basic plant parts Cotyledons are the first to emerge from the

soil. They are always opposite from each other on the stem, and may or may

hot be similar in form and shape to the later leaves. The first leaves can either

have an entire (smooth) or toothed (Iobed) leaf margin. The petiole is the plant

structure that attaches leaves or cotyledons to the main stem. Leaves will

either have pinnate (feather like) or palmate venation.

Slide 2: Cotyledon shape.

Slide 3: Linear, oblong, and lanceolate cotyledons. These cotyledons

can be differentiated from others by their linear shape. They are approximately

the same width the entire length of the cotyledon, and may or may not come

to a point at the tip. The cotyledon begins abruptly at the petiole.

Slide 4: Ovate cotyledons. The cotyledon is wider at the base and

always comes to a point at the tip. The cotyledon also begins abruptly at the

petiole.

Slide 5: Oval, round, and spatulate cotyledons. These cotyledons are

round. Oval cotyledons are slightly longer than wide, and never come to a

point at the tip. Round cotyledons do not come to a point at the tip. Both

begin abruptly at the petiole. Spatulate cotyledons are longer than they are

92

wide, but do not begin abruptly at the petiole. They never come to a point at

the tip. These cotyledons may have a slight indentation at the tip, similar to

a kidney shaped cotyledon.

Slide 6: Kidney shaped cotyledons. These cotyledons have a kidney

bean shape. The cotyledons begin abruptly at the petiole with a large dip at the

tip which gives the appearance of a kidney bean or alfalfa seed.

Slide 7: Leaf.

Slide 8: Leaf arrangement oh stem. Leaf arrangement can either be

opposite or alternate. If they are opposite, leaves emerge from the growing

point of the plant as a pair, this means there will be two leaves at the top of

the plant that are the same size 180° apart from each other on the stem. If the

leaves are alternate, leaves will emerge from the growing point of the plant one

at a time. There will always be one leaf that is smaller than the previous leaf

at the top of the plant. Often they are 90° apart from each other on the stem.

Slide 9: Leaf shape. Plants can either have Iobed or unlobed leaves. If

plants have a Iobed leaves, the Iobing can either be pinnate or palmate. Pinnate

Iobing is similar to a feather, with one main vein and the lobes deeply cut into

the leaf, sometimes almost to the vein. Palmate Iobing is similar to the palm

of your hand, with lobes radiating from a central point. If leaves are not Iobed,

the leaf margin can either be entire (smooth) or toothed. A toothed leaf margin

need not have lots of teeth (serrations). Often, there are only a few teeth.

Lambsquarters serves as a good example.

93

Slide 10: Stem shape. Stems can either be square or round. Roll the

seedling between your fingers. If it rolls easily, the stem is round, if it bumps

or jerks as it rolls, the stem is square. You can also cut the stem and look at

it in cross-section. If you see corners, the stem is square. If not, it's round.

After looking at the slides which describe how to use the key, pass out

the keys so the participants can examine the key with you. If you pass out the

keys prior to showing the slide set, the participants will examine the key and

ignore you. After participants have a key, point out that all of the information

presented in the slide set is found on the inner flaps of the key. Additional

information including definitions and suggestions for collecting seedlings for

identification are also found on the inner flaps of the key. Open the key and

show the participants how to use it. Identify the cotyledon shape, and move

across the key until a plant is identified. If the descriptions are not closelt

matching the specimen, the wrong cotyledon group may have been selected,

a common mistake for participants.

L

94

Seedling Slides:

■ /

Wild Mustard: The only plant on key with kidney shaped cotyledons. Easiest

to key out. Do this plant first so participants have an initial success.

Cowcockle: Linear cotyledons, leaves not pinnately lobed, leaves sparsely hairy

or without hair, leaves opposite, leaves not needle-like, leaves not mealy.

Catchweed Bedstraw: Oval cotyledons, stem is square above the cotyledons,

leaves are whorled with 4 to 8 per node. Plant is sticky like velcro.

Russian Thistle: Linear cotyledons, leaves not pinnately lobed, leaves sparsely

hairy or without hair, leaves are opposite, leaves are needle-like. .

Henbit: Round cotyledons, stem is square above the cotyledons, leaves are

opposite with two leaves per node. Mature plant has small purple flowers that

occur in a whorl around the stem at the base of each set of leaves.

Eastern Black Nightshade: Ovate cotyledons, ovate-shaped leaves with pinnate

venation, leaves sparsely hairy or without hair. It is important to notice where

the hair is located. This nightshade has most of the hair on the stem, petiole,

and leaf margins. There is a small amount of hair On the leaf surface, but most

of the hair is located on the stem.

Redroot Pigweed: Linear cotyledons, leaves not pinnately lobed, leaves

sparsely hairy or without hair, leaves are alternate, leaves are not arrowhead

shaped, ovate-shaped leaves. Has an erect growth habit and also has a red

stem.

95

Pinnate Tansv Mustard: Linear cotyledons, leaves are pinnately Iobed, first two

leaves are opposite, later leaves are alternate. Very difficult to tell when plants

are small. It is easier to match the picture to the end of a leaflet. All these

drawings are very close to what the actual plant looks like. This weed is often

confused with flixweed.

Field Pennvcress: Oval cotyledons, stem is round or absent (forms a basal

rosette), Margin of second and later leaves is unevenly toothed or lobed, leaf

margin teeth are not spine tipped, leaves without hair. This seedling is on the

key twice due to the wide variation between seedlings. If the choice of margin

of second and later leaves is entire or evenly toothed was made, continue

through the key making the following choice - leaves without hair. A good■"v,

diagnostic tool to use for this one is to rub a leaf and smell the unpleasant odor

produced. This is a very distinct characteristic of field penny cress whick is)

called stink weed in some areas.

NOTE: If the margin of second and later leaves is to be evenly toothed or

lobed, then the leaf margin teeth must be mirror images of the other side of the

leaf. Teeth must occur at the same location on the leaf and be the same size

and shape.

Wild Buckwheat: Linear cotyledons, leaves not pinnately lobed, leaves sparsely

hairy or without hair, leaves are alternate, leaves are arrowhead shaped. This

weed is often confused with field bindweed. There are some important

differences: Wild buckwheat has linear cotyledons, is an annual with a single

96

root, grows scattered around the field, flowers are small and green, and the

seeds are black and triangular shaped. Field bindweed has kidney shaped

cotyledons, is a perennial with a rhizomatous root system, grows in large

patches, flowers are large trumpet shaped and can be different colors ranging

from white, pink, and lavendar, seeds are round and grey.

Kochia: Linear cotyledons, leaves not pinnately lobed, leaves are very hairy.

This weed tumbles and frequently gets caught in fence rows.

Corn Gromwell: Spatulate cotyledons (may have small dimple in end of

cotyledon, but is not large enough to fit into the kidney shaped cotyledon

category), stem is round, margin of second and later leaves is entire or evenly

toothed, leaves are hairy, cotyledons are densely hairy. Many people will not

read the key carefully and mistakenly call this one common sunflower. This

mistake is made because of the hairiness of the cotyledons.

Common Lambsouarters: Linear cotyledons, leaves are not pinnately lobed

(there may be leaf margin teeth, but leaves are not lobed), leaves are sparsely

hairy or without hair, leaves are opposite, leaves are not needle-like, leaves are

mealy. Mealy is listed in the definition list. May also be defined as having a

. frosty appearance, like a frosty window pane.

Common (Wild) Sunflower: Spatulate cotyledons, stem is round, margin of

second and later leaves is entire or evenly toothed (leaf is hairy, but leaf margin

is entire), leaves are hairy,,cotyledons are sparsely hairy or without hair. Often

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confused with corn gromwell. Make sure participants read key carefully. May

also rub a leaf and detect an odor characteristic of sunflowers.

Prickly Lettuce: Oval cotyledons, stem is round or absent (forms a basal

rosette), margin of second and later leaves is unevenly toothed or Iobed (leaf

margins are not mirror images of each other), leaf margin teeth have soft spines

at the tips. Spines are slightly larger than hairs and if they were stiff, would

poke, when touched (like a cactus).

Sheoerdsourse: Oval cotyledons, stem is round or absent (forms a basal

rosette), margin of second and later leaves is unevenly toothed or lobed, leaf

margin teeth are not spine tipped, leaves are hairy. This weed, like tumble

mustard (Jim Hill mustard, tall mustard) is very difficult to identify at this stage.

Sheperdspurse leaves have a narrower shape than tumble mustard. Tumble

mustard has longer, more obvious hairs on the leaf surface. The leaves also

have a wider shape.

Prostrate Pigweed: Linear cotyledons, leaves not pinnately lobed, leaves

sparsely hairy or without hair, leaves are alternate, leaves are not arrowhead

shaped, leaves are spatulate-shaped. (no abrupt beginning at the petiole).

Prostrate growth habit, often confused with common purselane which has

fleshy leaves, similar to jade plants.

MONTANA STATE UNIVERSITY LIBRARIES

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TEACHING WEED SEEDLING IDENTIFICATION AND CROP

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